Patent Publication Number: US-8541673-B2

Title: Hammer stoppers for pianos having acoustic and silent modes

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 12/429,485, filed Apr. 24, 2009, now allowed, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to hammer stoppers and use thereof in pianos playable in both acoustic and silent modes. 
     BACKGROUND 
     An acoustic piano employs distinct and separate systems to transfer energy from a finger or actuator input force into an auditory, vibrational force. The transmission system, commonly called “the action”, is a network of levers, cushions and hammers that accepts finger/actuator input force through a collection of pivotal levers, known as “keys”. The keys and action focus this input force into rotating hammers of proportional density that are positioned to strike against tensioned wire strings. Both hammers and their corresponding strings are carefully constructed to match their acoustic properties, resulting in a tapered or graduated “scale” of components that cumulatively produce a multiple note span of musical frequencies. The strings act as medium through which vibrational energy is transferred into an amplifier, such as a soundboard or electric speaker, where it ultimately is converted into audible sound. 
     Pianos can produce a wide range of volume. Large pianos can further expand this range to include very loud sounds, as heard in concert pianos that are constructed to broadcast over an orchestra without the assistance of electric amplification. Pianos are prevalent in many cultures worldwide. They are present in many households, schools, institutions, etc. Inevitably, this proximity of volume-producing instruments creates situations where sound control and sound reduction are necessary. Many piano manufacturers provide muting mechanisms within their pianos to selectively restrict volume level. These mechanisms typically include a rotating rail that temporarily places an impact-absorbing material of varying density between the hammers and strings. 
     SUMMARY 
     According to one aspect of the disclosure, a piano hammer stopper system comprises a stopper rail set comprising at least a first stopper rail member and a second stopper rail member, each movable between respective first positions, allowing unobstructed movement of associated piano hammers, and respective second positions, stopping at least one associated piano hammer from striking any corresponding string; at least one drive shaft rotatably coupled to one or both of the first and second stopper rail members of the stopper rail set; a drive arm attached to the at least one drive shaft and engaging a drive fulcrum; and at least one travel guide directing movement of one or both of the first and second stopper rail members of the stopper rail set between respective first and second positions; wherein rotation of the at least one drive shaft rotates the drive arm to engage the drive fulcrum for moving one or both of the first and second stopper rail members of the stopper rail set between its respective first and second positions. 
     Implementations of this aspect of the disclosure may include one or more of the following features. The at least one drive shaft is coupled to both the first and second stopper rail members of the stopper rail set, and both first and second stopper rail members are moved in unison between respective first and second stopper positions. The at least one drive shaft comprises: a first drive shaft coupled to the first stopper rail member of the stopper rail set, and a second drive shaft coupled to the second stopper rail member of the stopper rail set, and the first and second stopper rail members are moved independently between respective first and second stopper positions. The drive arm defines a slot configured to receive the drive fulcrum, the drive arm pivoting about and sliding with respect to the received drive fulcrum. The drive arm comprises first and second drive arm portions slidably engaging one another, the first drive arm portion attached to the stopper rail, and the second drive arm portion pivotally coupled to the drive fulcrum. The at least one travel guide comprises at least one guide shaft received by a guide way, the at least one guide shaft attached to at least one of the first and second stopper rails of the stopper rail set and at least one support member of the hammer stopper system. The at least one travel guide defines a guide way configured to receive the at least one drive shaft. At least one of the first and second stopper rail members of the stopper rail set is biased toward one of its respective first and second positions. The at least one drive shaft is flexible for following the general shape of the stopper rail set. The piano hammer stopper system further comprises a shaft rotator coupled to the at least one drive shaft for rotating the at least one drive shaft. The shaft rotator comprises a lever defining an aperture for a receiving a pivot, rotation of the lever about the pivot moving the at least one drive shaft vertically with respect to the pivot and rotating the drive shaft with respect to the stopper rail set. The piano hammer stopper system further comprises an arm rotator coupled to the drive arm for pivoting the drive arm with respect to the drive fulcrum. The first and second stopper rail members are supported by robust mounting brackets and linkage hardware designed and constructed to resist deflection and/or displacement of associated first and second stopper rails members when struck by one or multiple piano hammers during silent play mode. The first and second stopper rail members are supported at inner, opposed ends by an additional robust mounting bracket disposed therebetween, with additional linkage hardware extending between the additional mounting bracket and each of the opposed stopper rail member ends. The stopper rail set, or at least one of the first and second stopper rail members of the stopper rail set, varies along its length in a manner to cause feel of a piano key strike against a stopper rail in silent play mode to vary along the length of the stopper rail replicating variation in feel of piano key strike against strings of the piano in acoustic play mode along the length of a piano action. The stopper rail set varies along its length in one or more characteristics selected from among: dimension, shape, mass, stiffness, associated mounting bracket, linkage hardware dimensions, type, thickness, and effectiveness of padding. 
     According to another aspect of this disclosure, a piano playable in an acoustic mode and a silent mode comprises a series of keys; a series of key actions, each key action actuated by depression of a corresponding key; a series of rotatable hammers, each rotatable hammer defining a forward throw direction and having at least one corresponding string, the hammers being driven by corresponding key actions transferring forces from corresponding keys; and a hammer stopper system comprising a stopper rail set comprising a first stopper rail member and a second stopper rail member, each movable between a respective first position, allowing unobstructed movement of associated piano hammers, and a respective second position, stopping at least one associated piano hammer from striking any corresponding string; and at least one rail actuator assembly coupled to at least one of the first stopper rail member and the second stopper rail member of the stopper rail set, the at least one rail actuator assembly comprising at least one drive shaft rotatably coupled to one or both of the first and second stopper rail members of the stopper rail set; a drive arm attached to the at least one drive shaft and engaging a drive fulcrum; and at least one travel guide directing movement of one or both of the stopper rail members of the stopper rail set between its respective first and second positions; wherein rotation of the at least one drive shaft rotates the drive arm to engage the drive fulcrum for moving one or both of the stopper rail members of the stopper rail set between its respective first and second position. 
     Implementations of this aspect of the disclosure may include one or more of the following features. The at least one drive shaft is coupled to both the first and second stopper rail members of the stopper rail set, and both first and second stopper rail members are moved in unison between respective first and second stopper positions. The at least one drive shaft comprises: a first drive shaft coupled to the first stopper rail member of the stopper rail set, and a second drive shaft coupled to the second stopper rail member of the stopper rail set, and the first and second stopper rail members are moved independently between respective first and second stopper positions. The drive arm defines a slot configured to receive the drive fulcrum, the drive arm pivoting about and sliding with respect to the received drive fulcrum. The drive arm comprises first and second drive arm portions slidably engaging one another, the first drive arm portion attached to the stopper rail, and the second drive arm portion pivotally coupled to the drive fulcrum. The at least one travel guide comprises at least one guide shaft received by a guide way, the at least one guide shaft attached to at least one of the first and second stopper rail members of the stopper rail set and at least one support member of the hammer stopper system. The at least one travel guide defines a guide way configured to receive the at least one drive shaft. At least one of the first and second stopper rail members of the stopper rail set is biased toward one of its respective first and second positions. The at least one drive shaft is flexible for following the shape of the stopper rail set. The piano further comprises a shaft rotator coupled to the drive shaft for rotating the at least one drive shaft. The shaft rotator comprises a lever defining an aperture for a receiving a pivot, rotation of the lever about the pivot moving the drive shaft vertically with respect to the pivot and rotating the drive shaft with respect to the stopper rail set. The piano further comprises an arm rotator coupled to the drive arm for pivoting the drive arm with respect to the drive fulcrum. The piano further comprises a mode selection switch in communication with the at least one rail actuator assembly and controlling movement of the first and second stopper rail members of the stopper rail set between the respective first and second positions. The mode selection switch is engaged by a pedal of the piano. The piano further comprises a controller in communication with the at least one rail actuator assembly and controlling switching between the acoustic play mode and the silent play mode. The first and second stopper rail members are supported by robust mounting brackets and linkage hardware designed and constructed to resist deflection and/or displacement of associated first and second stopper rails members when struck by one or multiple piano hammers during silent play mode. The first and second stopper rail members are supported at inner, opposed ends by an additional robust mounting bracket disposed therebetween, with additional linkage hardware extending between the additional mounting bracket and each of the opposed stopper rail member ends. The stopper rail set varies along its length in manner to cause feel of a piano key strike against a stopper rail in silent play mode to vary along the length of the stopper rail replicating variation in feel of piano key strike against strings of the piano in acoustic play mode along the length of a piano action. At least one of the first and second stopper rail members of the stopper rail set varies along its length in manner to cause feel of a piano key strike against a stopper rail in silent play mode to vary along the length of the stopper rail replicating variation in feel of piano key strike against strings of the piano in acoustic play mode along the length of a piano action. The stopper rail set varies along its length in one or more characteristics selected from among: dimension, shape, mass, stiffness, associated mounting bracket, linkage hardware dimensions, type, thickness, and effectiveness of padding. 
     According to yet another aspect of this disclosure, a hybrid upright piano having selectable silent play mode and acoustic play mode comprises: a stopper rail selectably moveable between blocking and non-blocking positions, the stopper rail associated with mounting brackets at opposite ends by stopper rail adjustment screws disposed for rotation in horizontal arrangement relative to the mounting brackets with exposed screw heads fixed axially and rotatable at the mounting bracket, and with a body disposed in threaded engaged with the stopper rail and an associated locknut mounted thereto, wherein rotation of the exposed screw head with a tool disposed horizontally and in general axial alignment with the threaded screw body acts, by threaded engagement of the screw body and stopper rail and locknut, to adjust a horizontal position of the stopper rail relative to an opposed piano string plane for stopping piano key strike against associated piano string during silent play mode. 
     Implementations of this aspect of the invention may include the following feature. The hybrid upright piano further comprises a travel guide mounted to the piano action and defining a generally horizontal surface disposed to slidably support stopper bar movement between blocking and non-blocking positions. 
     According to yet another aspect of this disclosure, a method for adjusting stopper rail position in a hybrid upright piano having selectable silent play mode and acoustic play mode, comprising the steps of: selecting silent play mode to place a stopper rail in silent play stopper position; with one hand, holding a piano hammer against the stopper rail; using the other hand to turn a screwdriver in engagement with a screw head an axially fixed, rotatable adjustment screw in threaded engagement with the stopper rail and associated locknut mounted thereto; watching as spacing between the held piano hammer and the piano strings changes while the adjustment screw is turned; continuing to turn the screwdriver in either direction until desired spacing is achieved; and completing adjustment by discontinuing screw turning. 
     The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a grand (horizontal) piano with a hammer stopper system of the disclosure. 
         FIG. 2  is a side view of a grand piano action with a hammer stopper system of the disclosure. 
         FIG. 3  is a side view of an upright piano with a hammer stopper system of the disclosure. 
         FIG. 4  is a perspective view of a hammer stopper system of the disclosure for a grand piano. 
         FIG. 5  is a front perspective view of a hammer stopper rail assembly of the disclosure, e.g. for an upright piano, and  FIGS. 5A and 5B  are face views of separate hammer stopper rails for the bass section of the upright piano and the a treble section of the upright piano, respectively. 
         FIG. 6  is front perspective view of a hammer stopper rail frame assembly of the disclosure for an upright piano, while  FIG. 6A  is an enlarged front perspective view of an end mounting bracket of the hammer stopper rail frame assembly of  FIG. 6 . 
         FIG. 7  is a front perspective view of a hammer stopper rail assembly of the disclosure for an upright piano, while  FIG. 7A  is an enlarged front perspective view of an additional mounting bracket and linkage hardware for the mid-scale position of the hammer stopper rail assembly of  FIG. 7A . 
         FIG. 8  is rear perspective view of the hammer stopper rail assembly of  FIG. 7 , while  FIG. 8A  is an enlarged rear perspective view of the additional mounting bracket and linkage hardware for the mid-scale position of the hammer stopper rail assembly of  FIG. 7A . 
         FIG. 9  is a side view of a hammer stopper system of the disclosure for a grand piano in an acoustical mode/non-stopper position. 
         FIG. 10  is a side view of the hammer stopper system of  FIG. 9  in an intermediate position. 
         FIG. 11  is a side view of the hammer stopper system of  FIG. 9  in a silent mode/stopper position. 
         FIG. 12  is a side view of a hammer stopper system of the disclosure in an acoustical mode/non-stopper position. 
         FIG. 13  is a side view of a hammer stopper system in a silent mode/stopper position. 
         FIG. 14  is a perspective view of a hammer stopper system of the disclosure for a grand piano. 
         FIG. 15  is a perspective view of a hammer stopper system of the disclosure for a grand piano. 
         FIG. 16  is a perspective view of a hammer stopper system of the disclosure for an upright piano. 
         FIG. 17  is a perspective view of a hammer stopper assembly of the disclosure for an upright piano, and  FIG. 18  is a side view of an adjustable stopper rail mounting bracket for the hammer stopper assembly of  FIG. 17  (including the action bracket, which is not shown in  FIG. 17 ). 
         FIG. 19  is a somewhat diagrammatic side view of a piano hammer in engagement with a first stopper rail arrangement in a hammer stopper rail assembly of the disclosure, e.g. for an upright piano, and  FIGS. 19A through 19I  showing side section views of other examples of stopper rail arrangements for the hammer stopper rail assembly of the disclosure. 
         FIG. 20  is a perspective view of another hammer stopper assembly of the disclosure for an upright piano, and  FIGS. 20A and 20B  are side views of an adjustable stopper rail mounting bracket for the hammer stopper assembly of  FIG. 20  with the stopper bar in a forward (non-stopper) position on the travel guide and in a rearward (stopper) position on the travel guide, respectively. 
         FIG. 21  is a side view of a mode selection switch, e.g. for a grand piano. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     The present disclosure provides a hammer stopper system that may be incorporated in grand (horizontal) and upright pianos. In some configurations, as described below, the hammer stopper system can be retrofit into existing pianos, and/or removed, e.g., for ease of maintenance. Implementations of the hammer stopper system of this disclosure are illustrated for a grand piano, e.g., in  FIGS. 1 ,  2 ,  4 ,  9 - 15 , and  21 , and for an upright piano, e.g., in  FIGS. 3 ,  5 - 8 , and  16 - 20 . 
     Referring to  FIGS. 1-3 , a piano  100 ,  100 A (grand piano),  100 B (upright piano) playable selectively in an acoustic mode and a silent mode, includes a series of keys  110  and corresponding key actions  120  linked to rear ends  113  of the keys  110 . Each key action  120  is actuated by depressing a corresponding key  110 . A series of rotatable hammers  130 , each defining a forward throw direction, T, are driven by corresponding key actions  120 , which transfer forces from corresponding pressed keys  110 . Each hammer  130  is aligned to strike a corresponding string  140 , or group of strings  140 ′, upon being thrown. For example, the hammer  130  may strike between one and three strings  140 ,  140 ′ to provide the desired note of the corresponding depressed key  110 . For note  1  to notes  8  (or  10  or  12 , depending on the piano size), the strings  140  per hammer  130  may be unichords, meaning one string per note. For approximately note  11  to note  20  (or  30 ) or any note therebetween, depending on the piano scale, the strings  140  per hammer  130  may be bichords, meaning two strings  140  per note. For note  20  (or  30 ) through to note  88 , depending on the piano scale, the strings  140  per hammer  130  may be trichords, meaning three strings  140  per note. As such, when referring to a string  140 , as in a corresponding string  140  of a hammer  130 , it may include a group or set of strings  140 ′ (e.g., one or more strings  140 ). 
     Referring to  FIGS. 1 and 2 , in an exemplary grand (e.g. horizontal) piano  100 A, each key  110  is supported at a fulcrum  112 , and the rear end  113  of each key  110  may support a backcheck (not shown). A wippen lever  115  is pivotally connected to a structural assembly of the piano  110 A for pivoting about pivot  116 . A jack  122  is pivotally connected to the wippen lever  115 . An adjustable capstan  117 , attached to the key  110 , contacts a wippen butt  118  on the wippen lever  115  and raises the wippen lever  115  when the key  110  is depressed. The raised wippen lever  115  causes the jack  122 , in contact with a hammer knuckle  123 , to pivot an associated hammer  130 , which is pivotally connected to a hammer flange  126 . Further motion of the wippen lever  115  causes the jack  122  to move out of contact with the hammer knuckle  123 , i.e. to disengage, as the hammer  130  is thrown along a throw direction, T, for striking a corresponding string  140  or set of strings  140 ′. 
     Referring also to  FIG. 3 , in an exemplary upright piano  100 B, each hammer  130  includes a hammer shank  132 , a butt  134  attached to a first end  131  of the shank  132 , and hammer  130  attached to an opposite, second end  133  of the shank  132 . A depressed or actuated key  110  causes a jack  122  of the associated key action  120  to kick the butt  134  of the hammer  130 . When the jack  122  kicks the butt  134 , the butt  134  and the hammer shank  132  are driven for rotation toward the associated strings  140 . The hammer  103  strikes the string(s)  140 , producing an acoustic sound. When the keys  110  are in a rest position (e.g. when a player is not pressing the keys  110 ), the hammers  130  remain in home positions, resting on a hammer resting rail  138  and/or the jack  122 . 
     Referring to  FIGS. 2 and 3 , a hammer stopper system  200 ,  200 A (for a grand piano),  200 B (for an upright piano) includes a stopper rail  210  disposed between the hammers  130  and the strings  140 , and a rail actuator assembly  220  configured to move the stopper rail  210  between a first position, allowing unobstructed movement of the hammers  130 , and a second position stopping at least one hammer  130  from striking its corresponding string(s)  140 . For example, in a grand piano, the rail actuator assembly  220  moves the stopper rail  210  to the first position ( FIGS. 9 and 12 ) for acoustic play and to the second position ( FIGS. 11 and 13 ) for silent play. In some implementations, as with grand pianos  100 A ( FIG. 2 ), the hammer stopper system  200 ,  200 A is disposed substantially between the hammers  130  and strings  140 . In other implementations, as with upright pianos  100 B ( FIG. 3 ), portions of the hammer stopper system  200 ,  200 B are disposed on both sides of the hammers  130  with respect to the strings  140 . 
     The hammer stopper system  200 A (e.g. for a grand piano) includes a rail actuator assembly  220 A with a drive shaft  230  disposed along the stopper rail  210 . The drive shaft  230  rotates with respect to the stopper rail  210  and may be a rigid shaft (e.g., bar stock) or a flexible shaft, which transmits rotation and torque while remaining flexible to bend along any curves of the stopper rail  210 . In some examples, the drive shaft  230  is routed through or along a channel  212  ( FIG. 12 ) defined by the stopper rail  210 . The channel  212  may be an open or enclosed channel or throughway. The rail actuator assembly  220  includes at least one drive arm assembly  225  disposed along the drive shaft  230 . The stopper rail  210  may be have a break in continuity, flex joint, or other device for allowing flexing of the stopper rail at the drive arm assembly  225 , as discussed in more detail below. The drive arm assembly  225  includes a drive arm  240  attached to the drive shaft  230  and slidably coupled to a support member  300 , which may be attached to a pin block  303  or an action bracket  304 . Rotation of the drive shaft  210  causes rotation of the drive arm  240 , which engages a drive arm fulcrum  244  to move the stopper rail  210  between its first (non-stopper) position and its second (stopper) position. The drive arm fulcrum  244  may be disposed on a mounting bracket or support member  300 . The support member  300  may be attached to a pin block  303  or an action bracket  304 . The rail actuator assembly  220 A includes one or more travel guides  260  configured to guide movement of the stopper rail  210  along a travel path between its first and second positions. In the example shown, the travel path is a substantially linear path, while in other implementations, the travel path may be parabolic or non-linear. The stopper rail  210  may include a hammer cushion  211  ( FIG. 12 ) positioned to receive and absorb the impact of a thrown hammer  130 . 
     Referring to  FIG. 4 , the rail actuator assembly  220 A (e.g., for a great piano) includes a shaft rotator  250  coupled to the drive shaft  230  for rotating the drive shaft  230  and the attached drive arm(s)  240  between first and second positions for moving the stopper rail  210  between its corresponding first and second positions. Examples of the shaft rotator  250  include a lever  250 A coupled to the drive shaft  230  and pivoted by an attached wire  270  or linkage, a rotary actuator (e.g., rotary motor) (not shown) coupled to the drive shaft  230 , or a linear actuator, such as a solenoid. In examples using the lever  250 A, the wire or linkage  270  may be coupled to a mode selection switch  150  (e.g.,  FIG. 17 ) or pedal  160  (e.g.,  FIG. 1 ) of the piano  100 . In the example shown in  FIG. 4 , the lever  250 A is attached to the drive shaft  230  for transferring rotation to the drive shaft  230 . The lever  250 A defines an aperture  252  for receiving a pivot  254  about which the lever  250 A rotates. The pivot  254  may be attached to or defined by a portion of the piano case  105 , a plate horn of the piano  100 A, or a mounting bracket  300 , which may be attached to the pin block  303  or an action bracket  304 . A spring  256  may bias the lever  250 A to rotate the drive shaft  230  and move the stopper rail  210  toward one of its first or second positions. The spring  256  may be attached to a portion of the piano case  105 , a plate horn of the piano  100 A, or a mounting bracket  300 , which may be attached to the pin block  303  or an action bracket  304 . Actuation of the attached wire  270  (e.g., by the mode selection switch  150 A ( FIG. 17 )) moves the lever  250 A for actuating the rail actuator assembly  220 A. Rotation of the lever  250 A about its pivot  254  moves the drive shaft  230  vertically along an arcuate path with respect to the pivot  254  and rotates the drive shaft  230  with respect to the stopper rail  210 . The vertical movement of the drive shaft  230  with respect to the pivot  254  by the lever  250 A moves the stopper rail  210  between its first and second positions at the lever  250 A. The rotation of the drive shaft  230  by the lever  250 A causes rotation of each drive arm  240  of each drive arm assembly  225  to engage its corresponding drive arm fulcrum  244  to move the stopper rail  210  between its first and second positions at each drive arm assembly  225 . Each travel guide  260  maintains a vertical orientation of the stopper rail  210 , thus preventing rotation of the stopper rail  210  about its longitudinal axis, as it moves vertically between its first and second positions. 
     In some implementations, e.g. for a grand piano, the hammer stopper system  200 A is installed in a bass section of the piano  100 A (e.g., approximately between notes  1  and  21 ) and also separately installed in a treble section of the piano  100 A (e.g., approximately between notes  21  and  88 ). For example, referring to  FIG. 4 , a segment  201 A of the hammer stopper system  200 A in the bass section of the grand piano  100 A is shown, including the shaft rotator  250  (e.g., lever arm  250 A) that is substantially near note  1  and one drive arm assembly  225  that is substantially near note  21 . The segment of the hammer stopper system in the treble section of the piano (not shown) may include the shaft rotator substantially near note  21  and drive arm assemblies substantially near notes  51 ,  69 , and  88 . In another implementation, the shaft rotator  250  for the treble section of the piano may be substantially near note  88 , and the drive arm assemblies  225  may be substantially new notes  21 ,  51 , and  69 . In yet another implementation, the shaft rotator  250  for the treble section of the piano and the shaft rotator  250  for the bass section of the piano both may be substantially near note  21 , and the drive arm assemblies  225  may be substantially new notes  1 , and near note  51 ,  69 , and  88 . The shaft rotators  250  of the bass and treble segments and of the hammer stopper system  200 A may be actuated in unison or independently of each other for silent or acoustic play of the respective piano sections. 
     In other implementations of this disclosure, e.g., for an upright piano, referring to  FIGS. 5 ,  5 A, and  5 B, in another implementation of this disclosure, a first segment  201 B of the hammer stopper system  200 B is installed in a bass section of the upright piano  100 B (e.g., approximately between notes  1  and  21 ) and a second segment  203 B of the hammer stopper system  200 B is installed separately in a treble section of the upright piano  100 B (e.g., approximately between notes  26  and  88 ). The hammer stopper rail system  200 B has two separate hammer stopper or stopper rails  210 ,  210 ′. In the implementation shown in the drawings, both rails are linked to a common actuation mechanism, but the stopper device itself, i.e. hammer stopper rail that directly receives the impact from piano hammers, is separated into two metal bars, i.e. bass section bar  210  and a treble section bar  210 ′, each with a cushioned impact surface  211  positioned for engagement with the hammer shank  132 . The bass section bar  210  (of length “L bass ”) spans the bass section of the piano action, typically from notes  1  through  26  (or  1  through  27 , or  1  through  34 , etc.). The treble section bar  210 ′ (of length “L treble ”) spans a longer remaining region of the piano action, from low treble through high treble, typically from notes  27  through  88  (or from  28  through  88  or = 36  through  88 , etc.). In one implementation, stopper rail bars  210 ,  210 ′ are steel bars with rectangular cross section, e.g. about 10 mm by 12 mm, disposed to extend horizontally in a region located just below the white felt hammers  130 . The stopper rails may be attached to the supporting frame-linkage system  200 B only at the ends of the rails, and thus could be considered “simple beams.” The location  213  between the two stopper rails is called “the bass-treble nor break” or just “the break.” In other implementations, a mounting bracket  300  is located at the mid-treble location, with the mounting bracket  300  supporting the drive shaft  230 . In one arrangement, a linkage assembly  302  may also be provided at this location, which means a total of three linkages  302  on the treble stopper bar  210 ,  210 ′, which can have the disadvantage of both shortening the effective beam length and making it relatively more difficult to adjust the position of the stopper bar  210 ,  210 ′ relative to the plane of the strings  140 ,  140 ′ (see discussion of  FIGS. 17 and 18  below). Alternatively, in another arrangement, the linkage assembly  302  is omitted at the mid-treble location, which makes it relatively easier to adjust the position of the treble stopper bar relative to the strings, but also lengthens the effective beam length to be the full length of the rail  210 ,  210 ′ (see discussion below). 
     The relatively shorter beam lengths of the two, separate stopper rails  210 ,  210 ′ of this disclosure, each mounted at the ends, i.e., at notes  1  and  26 , and at notes  27  and  88 , respectively, results in relatively less beam deflection, e.g. compared to the relative length of standard one-piece bars. This arrangement differs from prior known hammer stopper rail systems, where the stopper rail is typically one continuous beam, extending from note  1  to note  88  and mounted only at the ends. The result is markedly less beam deflection, which means that stopper rail position can be regulated more closely, thereby minimizing the amount of piano action regulation compromises that are required, e.g. in manufacture and maintenance. This, in turn, permits the piano action “touch” to be better, in particular for more experienced and professional piano artists, and will make the piano easier to play well. 
     When the hybrid piano of this disclosure is played in silent mode, the piano hammers  130  strike (i.e., apply a force “f” to) the stopper rail  210  or  210 ′. During a typical 2- or 4-hand performance, multiple (“n”, where n&lt;=20) hammers strike the stopper rail simultaneously, applying a cumulative impact force “F” to the rail (F=n*f). This force “F” causes the stopper rail (“beam”) to deflect. The deflection can be calculated using the Euler-Bernoulli beam bending equations. In the simplified case of a central point load on a simply supported beam of length “L”, the equation for maximum deflection “w(max)” is:
 
ω max   =c*F*L   3  
 
     where c is constant. 
     Thus, the longer the hammer stopper rail “L” (length), the greater the maximum deflection “ω max ”. Conversely, the shorter the hammer stopper rail “L” (length), the smaller the maximum deflection “ω max ”. 
     Since a piano equipped with a stopper rail assembly of the present disclosure is constructed with two separate, relatively shorter stopper rails [of lengths “L bass ” and “L treble ”], the values of “L” in the above equation are similarly relatively smaller than in traditional one-piece rail designs [with length L 88 notes ]:
 
 L   88 notes   ˜L   bass   +L   treble  
 
Typically:
 
 L   bass =23 to 38% of  L   88 notes ;
 
and
 
 L   treble =77 to 63% of  L   88 notes .
 
     To calculate a representative deflection comparison, assuming that the cross-section and material properties of the stopper rails to be compared remain unchanged, and assuming a median distribution of stopper rail lengths of 30/70 for the bass/treble rails in the two-piece system. In the two-piece stopper rail system, the maximum deflection will occur in the middle of the longer treble rail, which has length:
 
 L   treble =77%* L   88 notes  
 
For the treble rail in the two-piece system,
 
ω max   =c*F *(0.7 *L   88 notes ) 3  
 
ω max =0.34 *F *( L   88 notes ) 3  
 
For the rail in the one-piece rail system,
 
ω max   =c*F *( L   88 notes ) 3  
 
Therefore:
 
ω max (two-piece stopper rail system)=0.34*ω max (one-piece stopper rail system)
 
     As the preceding calculation shows, the maximum deflection of either stopper rail  210 ,  210 ′ in the two-piece system is ˜34% of the maximum deflection of the stopper rail in the one-piece system. This smaller maximum deflection reduces the likelihood of the hammers accidentally striking the strings (and causing a sound) during forte playing in silent mode. This in turn allows the stopper rail assembly adjustment (regulation) to be brought closer to the string plane. 
     All hybrid pianos require action regulation (mechanical adjustment) compromises. These compromises detract from the desirable “feel” (mechanical responsiveness) of the action, because the action must be adjusted to function with an additional stop location (at the hammer stop rail, during silent mode), in addition to the normal hammer stop location (at the strings, during acoustic mode). The greater the rotational distance between the stopper rail  210 ,  210 ′ and the piano strings  140 ,  140 ′, the larger the action regulation compromise, the worse the action feels to the pianist, and the harder it is to play the piano well. Conversely, the smaller the rotational distance between the stopper rail  210 ,  210 ′ and the piano strings  140 ,  140 ′, the smaller the action regulation compromise, the better the action feels, and the easier it is to play the piano well. 
     Since the maximum deflection in a two-piece stopper rail system is approximately 34% of the maximum deflection in a one-piece stopper rail system, the stopper rails in the two-piece system can be set to be closer to the strings. This reduces the rotational distance between the stopper rail and the strings, and this reduced rotational distance means that the required action regulation compromises are smaller. The result is a better feeling action and a piano that is easier to play well. 
     Referring also to  FIGS. 6 and 6A  (from which the action parts, hammer stopper rails, and hammer stopper assembly linkages of the upright piano are omitted for greater visibility),  FIGS. 7 and 7A  and  FIGS. 8 and 8A  (from which the action parts are omitted for greater visibility), the hammer stopper rail  210 ,  210 ′ is mounted very securely upon mounting brackets  300  with linear linkage hardware assemblies  302  that are all exceptionally robust and strong in the front-to-back direction. 
     The stopper rail system  200 ,  200 B of the present disclosure includes an additional mounting bracket  300 ′ and two additional sets of linkage hardware  302 ′,  302 ″ in the interior of the scale (e.g., between notes  26  and  27 ), in the region of the “the bass-treble break” or “the break”  213 . This is in addition to the standard mounting brackets  300 , each with a single set of linkage hardware  302 , present at the beginning (note  1 ) and at the end (note  88 ) of the piano scale. In contrast, traditional stopper rail systems have mounting brackets only at note  1  and at note  88 , with no additional mounting bracket at the interior of the scale. Furthermore, the mounting brackets  300  supporting the stopper rail segments  210 ,  210 ′ are associated with linkage hardware assemblies  302 , consisting of adjustment screw  500  extending from threaded engagement (at screw end  508 ) with the stopper rail  210 ,  210 ′ and plastic locknut  510  mounted thereto, to axially fixed, rotational engagement (at screw head  502 ) with adjustment pivot block  504 , attached at pivot fulcrum connection  503  ( FIGS. 7A ,  8   a , and  18 ) with shaft hanger block  506  secured to drive shaft  230 . 
     The increased strength of the hammer stopper rail assembly mounting system  200 B of this disclosure, including especially the mounting brackets  300  and the linkage hardware assemblies  302 , results in more stationary stopper rail positioning. Even when the stopper rails  210 ,  210 ′ of this disclosure are struck repeatedly by up to 20 hammers at a time (e.g., in a typical 4-hand performance), the stopper rails barely move, because the mounting system is so strong; and because the stopper rails barely move when struck, the stopper rails can be positioned relatively closer to the string plane. This permits relatively reduced action regulation compromises, which, in turn, results in a better feeling action and a piano that is easier to play well. 
     In addition, the solidity of the stopper rails and the mounting system of the hammer stopper rail assembly system  200 B of the present disclosure reduces the amount of energy is that absorbed by the stopper rail system when struck by the piano hammers  130 . Instead, the piano hammers  130  are caused to bounce back at nearly their original velocity, transmitting an amount of energy back into the piano action  120  and the keys  110 , to replicate the reflective quality of an original acoustic piano action in which hammers  130  rebound from tensioned strings  140 ,  140 ′. 
     In some implementations, e.g. for a grand piano, as shown in FIGS.  4  and  9 - 15 , the drive arm  240  defines a guide way  242  (e.g., slot or groove) configured to receive the drive arm fulcrum  244 . Rotation of the drive shaft  230  in the clockwise or counter-clockwise direction causes the drive arm  240  to pivot and slide on the drive arm fulcrum  244  to move the stopper rail  210  between its first and second positions. In some implementations, as shown in  FIGS. 14 and 15 , the drive arm  240  includes first and second portions  241 ,  243  slidably engaging one another (e.g., telescopically). The first drive arm portion  241  is attached to the drive shaft  230  and the second drive arm portion  243  is pivotally attached to the drive arm fulcrum  244 . Rotation of the drive shaft  230  in the clockwise or counter-clockwise direction causes the drive arm  240  to pivot on and telescope to and from the drive arm fulcrum  244  to move the stopper rail  210  between its first and second positions. 
     In the examples shown in  FIGS. 9-14 , the travel guide  260  is configured as a guide shaft  260  attached to the stopper rail  210  and received through a guide way  262  (e.g., aperture or groove) defined by the support member with mounting bracket  300 . Similarly, the guide shaft  260  may be attached to the support member  300  and received through a guide way  262  defined by the stopper rail  210 . In the example shown in  FIG. 15 , the travel guide  260  is attached to a support member  300  and defines a guide way  262  (e.g., slot or groove) for receiving the drive shaft  230 , which is disposed on or through the stopper rail  210 . The travel guide  260  allows rotation of the drive shaft  230  and is disposed at each end of the stopper rail  210  for guiding movement of the stopper rail  210 . In the example shown in  FIG. 11 , the travel guide  260  includes a spring  266  for biasing the stopper rail  210  toward its second position for silent play. 
       FIGS. 3 ,  16 ,  18 , and  19  illustrate implementations of a hammer stopper system  200 ,  200 B for an upright piano  100 B. The hammer stopper system  200 B includes a stopper rail  210  disposed between the hammers  130  and the strings  140 , and a rail actuator assembly  220 B configured to move the stopper rail  210  between a first position, allowing unobstructed movement of the hammers  130 , and a second position stopper at least one hammer  130  from striking its corresponding string(s)  140 . The rail actuator assembly  220 B moves the stopper rail  210  to the first position for acoustic play and to the second position for silent play. In the example shown in  FIG. 16 , the rail actuator assembly  220 B includes a drive shaft  230  disposed along the stopper rail  210 . The drive shaft  230  may be a rigid shaft (e.g., bar stock) or a flexible shaft, which transmits rotation and torque while remaining flexible to bend along any curves of the stopper rail  210 . In some examples, the drive shaft  230  is routed through a channel  212  defined by the stopper rail  210 . The rail actuator assembly  220  includes at least one drive arm  240  attached to the drive shaft  230  and slidably coupled to a support member or mounting bracket  300 . Rotation of the drive shaft  230  causes rotation of the drive arm  240  which engages a drive arm fulcrum  244  to move the stopper rail  210  between its first and second positions. The drive arm fulcrum  244  may be disposed on a support member  300  (e.g., bracket). The rail actuator assembly  220 B includes a drive arm rotator  255  configured to pivot the drive arm  240  with respect to the drive fulcrum  244 . 
     The rail actuator assembly  220 B includes one or more travel guides  260  configured to guide movement of the stopper rail  210  along a travel path between its first and second positions. As with the grand piano system, the travel path may be a substantially linear or non-linear (e.g., parabolic). In the example shown in  FIG. 16 , the travel guide  260  includes first and second portions  261 ,  263  slidably engaging one another (e.g., telescopically) and providing a substantially linear travel path for the stopper rail  210 . The first travel guide portion  261  is attached to the stopper rail  210  and the second travel guide portion  263  is attached to the support member  300 . 
     Referring to  FIGS. 17 and 18 , a stopper rail assembly of the present disclosure for an upright piano  100 B is shown. In particular,  FIG. 17  is a perspective view of the hammer stopper assembly  200 B with the following elements removed for improved visibility: action bracket ( 304 , in  FIG. 18 ), damper lever assemblies, whippen assemblies, the portion of the hammer butt assemblies below the wooden butt molding, and mounting bracket for stopper rail. In  FIG. 17 , a set of piano hammers  130  are seen mounted on hammer shanks  132  extending from butts  134  mounted from hammer flanges  136  on the main action rail  310 , e.g., an aluminum extrusion. Damper stopper rail  312 , seen also in  FIG. 18 , is an aluminum bar covered with felt, which also serves as a cross-bar on which the mounting bracket  300  is hung. Referring now also to  FIG. 18 , the mounting brackets  300  supporting the opposite ends of the stopper rail  210  (indirectly via the linkage assemblies, and in the horizontal direction) are associated with linkage hardware assemblies  302 , consisting of adjustment screw  500  extending from threaded engagement (at screw end  508 ) with the stopper rail  210 ,  210 ′ and plastic locknut  510  mounted thereto, to axially fixed, rotational engagement (at screw head  502 ) with adjustment pivot block  504 , attached as pivot fulcrum connection  503  with shaft hanger block  506  secured to drive shaft  230 . This arrangement provides end-sectional adjustment screws  500  accessible at the front of the piano action  120 , at each end of the stopper rail  210 ,  210 ′. The screws, which permit adjustment of the position of the stopper rail  210 ,  210 ′ relative to the string plane  140 ,  140 ′ are mounted for axial adjusting motion in the stopper rail direction. The head  502  of each screw  500  is exposed at the front of the piano action  120  at the adjustment pivot block  504 , which extends from the shaft hanger block  506  below the drive shaft  230  on mounting bracket  300 . The screw head  502  is locked axially in the adjustment pivot block  504 , but not locked rotationally. When the screw head  502  is turned, e.g. by the blade of a screwdriver (not shown) aligned generally axially with the screw  500 , threaded screw body  508  rotates in tapped hole in the steel stopper rail  210 ,  210 ′ and nylon inset  510  (similar to a locknut) mounted on the back side of the stopper rail. In another implementation, the nylon insert or locknut has the form of a plastic cylinder  510 ′ (seen in dashed line in  FIG. 7A ) press fit into a vertical cylindrical holes formed in the top surface of stopper bars  210 ,  210 ′. As seen in the drawings, the screw  500  is disposed horizontally, with the adjustment screw head  502  thus being easily accessible with conventional tools. Adjusting rotation of the screw  500  causes a directly responsive movement of the stopper rail  210 , either forward or backward, depending on the direction of screw rotation, which makes precise adjustment of the position of the stopper bar  210 ,  210 ′ relative to the plane of the piano strings  140 ,  140 ′ as the horizontal screw  500  is turned by fractions of a turn, and since the locknut  510  is secured to the stopper rail  210 ,  210 ′, there is no late or accidental movement of the adjusted position. By way of example, with the stopper rail  210 ,  210 ′ in stopper (silent play) position, a technician may use one hand to hold a piano hammer  130  against the stopper rail  210 , and use the other hand to turn a screwdriver in engagement with the screw head  502 . Adjustment feedback is instantaneous, i.e., the technician can watch as spacing between the held piano hammer  130  and the strings  140 ,  140 ′ change while the adjustment screw  500  is turned. As mentioned above, the nylon insert or locknut  510  is built into the stopper rail  210 ,  210 ′, so no additional tightening or loosening is necessary. Feedback is instantaneous, and subsequent tightening or adjustment is not required. As a result, the ease of adjustment of the hammer stopper rail assembly system  200 B of the present disclosure permits a more accurate setting of the stopper distance from the string plane, and as the adjustment is being made, the piano action  120  remains functional, and the stopper distance can be accurately determined. 
     This arrangement differs from other piano adjustment systems, where adjustment screws may be accessible, but they are disposed vertically and accessed only indirectly, which makes it difficult to adjust the stopper rail brackets. For example, in one known implementation, three vertical screws must be loosened to permit re-positioning of an L-shaped bracket, then the vertical screws must be retightened while taking care that the L-bracket does not move before the screws are secure. The positioning must then be checked again, and the process repeated as necessary. 
     Referring also to  FIGS. 20 ,  20 A, and  20 B, in another implementation of the hammer stopper system of  FIGS. 17 and 18 , a travel guide  314  for the hammer stopper rail  210 ,  210 ′ is adjustably mounted to the damper stop rail  312  in the hammer stopper system  200 B for the upright piano  100 B. The travel guide  314  has the form of a bent wire body  316  covered by flexible tubing  318  of low friction, wear resistant material, e.g. polyethylene. The upper end portion  320  of the body  316  provides a generally horizontal surface  322  that supports the hammer stopper bar  210 ,  210 ′. The lower surface of the stopper bar, disposed in engagement with the surface  322 , is preferably covered with a low friction material, e.g. felt, and slides forward and backward (arrow S) on the plastic covered body  316  of the travel guide wire  314 , e.g. as the hammer stopper rail  210 ,  210 ′ is moved forward (closer to the strings  140 ,  140 ′) towards a non-blocking position ( FIG. 20A ) and backward (away from the strings  140 ,  140 ′) towards a blocking position ( FIG. 20B ). As in  FIG. 7A , the locknut has the form of a plastic cylinder  510 ′ press fit into a vertical cylindrical holes formed in the top surface of stopper bar  210 ,  210 ′. 
     In another implementation, mechanical properties, e.g., mass, stiffness, energy absorption, etc. of the piano hammer stopper rail system of the present disclosure are intentionally varied across the piano, in order to achieve desired piano performance characteristics across the full range of piano keys. The range of desired mechanical properties is achieved by intentional choices of, e.g., materials, size, shape, fasteners, etc. In a standard acoustic piano, hard felt hammers strike steel and copper/steel wire strings. In a hybrid piano, in silent mode, the hammer shanks strike the hammer stopper bar assembly instead of the hammers striking the piano strings. Differences between the materials that are struck, and between the rotational positions of the hammer and shank assembly when the strike occurs, tend to make the “action touch”, i.e. the feel of the action to the pianist&#39;s fingers, different. 
     An objective of the hammer stopper rail system of the present disclosure is to cause the difference in feel to the pianist to be as small as possible. The elements contributing to reaching this objective include, e.g., the two piece stopper rail, the massive stopper rail, the robust mounting structure, etc. Since piano string length and diameter, and hammer size and weight, vary from bass to treble, the “action touch” also varies from bass to treble. In the hammer stopper rail system of the present disclosure, some mechanical properties are intentionally designed to vary from bass to treble, in order to best match the mechanical properties of the acoustic piano action played in acoustic mode. 
     Referring to  FIG. 19  and to  FIGS. 19A through 19I , various, but non-exhaustive, examples of constructions and arrangements of stopper rail cross sections are shown, including variations in cushioning characteristics, materials, mechanical properties, dimensions, arrangements, etc., across range of the piano key positions. For example, in  FIGS. 19 and 19A , a stopper rail  210   a  has a metal rail body  600 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, faced with a relatively thin layer  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with a relatively thicker layer of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed therebetween. In  FIG. 19B , a stopper rail  210   b  has a metal rail body  600 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, faced with two relatively thin layers  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with a relatively thicker layer of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed between the thin layers  602  and the rail body  600 . In  FIG. 19C , a stopper rail  210   c  has a metal rail body  600 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, faced with a relatively thin layer  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with two relatively thicker layers of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed between the thin layer  602  and the rail body  600 . In  FIG. 19D , a stopper rail  210   d  has a metal rail body  600 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, faced with two relatively thin layers  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with two relatively thicker layers of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed between the thin layers  602  and the rail body  600 . In  FIG. 19E , a stopper rail  210   e  has a metal rail body  610 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, of different dimensions, faced with a relatively thin layer  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with a relatively thicker layer of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed between the thin layer  602  and the rail body  610 . In  FIG. 19F , a stopper rail  210   f  has a metal rail body  620 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, of other different dimensions, faced with a relatively thin layer  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with a relatively thicker layer of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed between the thin layer  602  and the rail body  620 . In  FIG. 19G , a stopper rail  210   g  has a cylindrical metal rail body  610 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, of different dimensions, faced with a relatively thin, curved layer  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with a relatively thicker, curved layer of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed between the thin layer  602  and the rail body  630 , forming a curved stopper surface  632 . In  FIG. 19H , a stopper rail  210   h  has a metal rail body  640 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, of different dimensions and an angled front (stopping) surface, faced with a relatively thin layer  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with a relatively thicker layer of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed between the thin layer  602  and the rail body  640 , the layers  602  and  604  having relatively uniform thickness, forming an angled stopper surface  642 . In  FIG. 19I , a stopper rail  210   i  has a metal rail body  650 , e.g. steel or other suitable metal, plastic, or other strong, rigid material, faced with a relatively thin layer  602  formed, e.g. of suitable sound and/or force absorbing material, e.g. any of felt, cloth, microfiber, leather, thin foam, etc., with a relatively thicker layer of suitable sound and/or force absorbing material  604 , e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., disposed between the thin layer  602  and the rail body  650 . The layer  602  in this implementation has relatively uniform thickness, while layer  604  has tapered thickness, with the larger thickness at the upper edge, forming an angled stopper surface  652 . 
     Many other implementations are also possible for the purpose of varying and/or customizing the performance characteristic of the hammer stopper rail assembly system  100 ,  100 A,  100 B across the range of the piano keys. For example, mounting bracket size, shape, material, quantity and/or location; linkage design; stopper rail location; mounting bracket location; etc., can be varied across the range of the piano in order to achieve the desired touch characteristics of the hammer stopper rail system in an acoustic piano action. In one implementation, the bass stopper rail  210  may have a relatively thicker layer of suitable sound and/or force absorbing material, e.g. any of relatively dense or softer foam, relatively dense or softer felt, etc., applied over the stopper surface of a metal rail body, while the treble stopper rail  210 ′ may a relatively thin layer formed of thin woven felt, with a relatively thicker layer of suitable sound and/or force absorbing material, e.g. thick dense foam disposed between the thin layer and the metal rail body of rectangular cross section (see, e.g.,  FIGS. 19 and 19A , as described above). In other implementations, construction of the stopper rails  210 ,  210 ′ may be changed at the middle, or other interval, of one or both of bass segment ( 201 A/ 201 B) and the treble segment ( 203 A/ 203 B). 
     These intentional variations across the 88 piano notes allow a hybrid piano to have touch characteristics that mimic, as closely as possible, the touch characteristics of an acoustic piano, across the entire piano. 
     Referring again to  FIGS. 1 and 3 , in some implementations, the piano  100 A,  100 B includes a mode selection switch  150  in communication with the rail actuator assembly  220 ,  220 A,  220 B (e.g., in communication with the shaft rotator  250  or the drive arm rotator  255 ). A user may toggle the mode switch  150  to alter the play mode between acoustic play and silent play, and the drive shaft  230  is rotated to the corresponding position of the play mode. In some implementations, the mode selection switch  150  is coupled to a wire or linkage  270  coupled to the rail actuator assembly  220  (e.g., via the shaft rotator  250  or the drive arm rotator  255 ). In other implementations, the mode selection switch  150  may be housed by a controller unit  400  ( FIGS. 1 and 3 ) disposed on the piano  100 A,  100 B. The controller  400  may include circuitry that controls switching between play modes (e.g. via the rail actuator assembly  220 ,  220 A,  220 B), storing play information (e.g. MIDI files), electronic play calibration, tone adjustment, and trouble shooting, inter alia. The controller  400  may be in communication with the drive shaft rotator  250  or the drive arm rotator  255  actuating the rail actuator assembly  220 . 
     The piano  100 A,  100 B may also include a mode selection switch  150 A, an example of which is shown in  FIG. 21 , disposed on a portion of a piano case  105  of the piano  100 A,  100 B. For example, the mode selection switch  150 A may be located on the piano case  105  below the keys  110  (e.g., on a vertical or horizontal panel). The mode selection switch  150 A includes a handle  152  pivotable between first and second positions. The wire  270  is attached to the handle  152  and guided through a sheath  272  to the shaft rotator  250 . In its first position, the mode selection switch  150 A causes the rail actuator assembly  220  of the hammer stopper system  200  to hold the stopper rail  210  in its first position allowing unobstructed movement of piano hammers  130 . In its second position, the mode selection switch  150 A causes the rail actuator assembly  220  to hold the stopper rail  210  in its second position stopper at least one piano hammer  130  from striking any corresponding strings  140 . The handle  152  may be releasably held in its first and second positions be a spring, magnet, releasable fastener (e.g., hook and loop fasteners), etc. In the example of a spring, a spring  266  may be attached to the handle and/or the rail actuator assembly  220 . In some examples, the handle  152  may be releasably held in its first and second positions by a detent, groove, or feature defined by the piano case  105  or a bracket holding the handle  152 . 
     In some implementations, the silent play mode is engaged by pressing a mode selection pedal  160  (e.g., by pressing the pedal  160  downward and then rotating it laterally to a lockably engaged position to hold the silent play mode). The mode selection pedal  160  is coupled to a cable or linkage  270  coupled to the rail actuator assembly  220  (e.g., via the shaft rotator  250  or the drive arm rotator  255 ). In some cases, the mode selection pedal  160  engages the mode selection switch  150  when moved to its engaged position. The mode selection pedal  160  may be held in its engaged position, e.g., by a magnet, detent in a piano casing, a bracket, etc. 
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, referring to  FIG. 4 , the spring  266  may instead be disposed, e.g. between the support member  300  and the stopper rail  210 , for biasing the stopper rail  210  toward its first position for acoustic play, or an extension spring may instead, or also, be employed. Accordingly, other implementations are within the scope of the following claims.