Abstract:
This invention relates to improvements to a stringed musical instrument, and more particularly to guitar design for use with transposing vibrato mechanisms. 
     Vibrato devices for guitars are known. The present device and method improve the ability to of a player to bend entire chords in a manner that maintains harmonic relationship between the individual strings. 
     The invention also included improved manual controls and means to extend the transposing range of such a vibrato device.

Description:
[0001]    This application claims priority to U.S. provisional application 61/529,910 filed Aug. 31, 2011, by the present applicant. 
         [0002]    This application is a continuation in part of U.S. non-provisional application Ser. No. 12/842,028 filed Jul. 22, 2010 by the present applicant, which claimed priority to U.S. provisional application 61/271,586 filed Jul. 22, 2009 and to PCT application U.S. Ser. No. 10/27736 filed Mar. 17, 2010. 
         [0003]    This application is a continuation in part of U.S. non-provisional application Ser. No. 12/283,668 filed Sep. 15, 2008 by the present applicant, which in turn claimed priority to U.S. provisional application 60/960,075 filed Sep. 14, 2007. 
         [0004]    The disclosure of this application incorporates by reference the entirety of said application Ser. Nos. 12/283,668 and 12/842,028. 
         [0005]    Said incorporation by reference shall supplement the present disclosure without in any way limiting the scope or meaning of the disclosure or claims of the present application or subsequent applications. 
     
    
     FIELD OF INVENTION 
       [0006]    The present invention relates to devices which enhance the expressive qualities of a stringed musical instrument by empowering the artist to “bend” notes and chords in a harmonic manner. 
       SUMMARY 
       [0007]    This application discloses various embodiments having guides adjustably fixed relative to a pivoting tailpiece, causing the strings to be stretched or relaxed when the tailpiece is rotated, enabling maintenance of relative pitch among strings. 
         [0008]    The application dicloses dual axis control, ebabling a musician to sweep easily from “bend” to “dive” (sharp to flat) while using the muscles on only one side of the hand and wrist. Dual axis control further allows biasing a tailpiece against a separate stop on a separate axis after either a bend or a dive, with enhanced stablity at neutral pitch, and requiring no locking mechanism. 
         [0009]    The application discloses various embodiments of a cam-enabled return spring to maintain neutral tuning when the device is released without adversely affecting motion of the device. 
         [0010]    Embodiments also include a beneficial combination of pitch-relative and non-pitch-relative vibrato means, where a non-pitch-relative vibrato displacement may be used to compensate for non-linearities in string tension while transposing over large spans. 
         [0011]    Also disclosed are various embodiments enabling improved electronic control, improved limitation on string stress, improved float about a neutral position, improved flex compensation, improved string anchoring, improved fulcrum support, and improved bending means for individual strings. 
     
    
     
       DRAWINGS 
         [0012]    Letters I and O are omitted from figure designations in the interest of clarity. 
           [0013]      FIG. 1A  shows an end view of an embodiment of a vibrato control arm having a rotational axis substantially parallel to the stings, where the body is cutaway to show an embodiment of vibrato connection and biasing means. 
           [0014]      FIG. 1B  show a top view of an embodiment of a vibrato control arm having a rotational axis substantially parallel to the stings, and of drum on an axis substantially parallel to the strings for manipulating an electronic rotation sensor. 
           [0015]      FIG. 1C  shows an end view of an embodiment of a vibrato control having a rotational axis substantially parallel to the stings, where the control comprises at least a partially arcuate surface. 
           [0016]      FIG. 1D  shows an end view of an embodiment of a vibrato control having a rotational axis substantially parallel to the stings, where the control arm comprises a substantially planar surface 
           [0017]      FIGS. 2A through 2H  and  2 J are side views of embodiments of alternative means of positioning a string guide about an arcuate path with respect to a rotating member. 
           [0018]      FIGS. 3   a  through  3   c  show side views of embodiments having means for limiting the stretch of a string to allow more extreme bends 
           [0019]      FIGS. 4A ,  4 B, and  4 C illustrate basic elements of flex compensation in examples where the members are string-engaging members are not necessarily articulated. 
           [0020]      FIGS. 5A through 5C  show progressive side views of a vibrato device having a cam enabled dive capability. 
       
    
    
     DESCRIPTION 
       [0021]    In this discussion, traditional, non-transposing vibrato action and components thereof shall be referred to as “standard”; e.g. standard dive, bias, bend, bias stop. Pitch-relative vibrato action and components thereof shall be referred to as “harmonic”; e.g. harmonic dive, bias, bend, bias stop. 
       Bias Limit Cam Notes 
       [0022]    In an embodiment of a bias cam and follower in  FIG. 5   c , at least a part of the cam surface  52  is configured to engage follower  54  at a location opposite a ray between the follower axis and the transport axis  58  from a handle of on the control arm  16 . Said location allows a small rotation of the control arm to effect a relatively larger displacement of transport  57 . In a preferred embodiment of this feature, the engagement crosses said ray during the initial rotation of the arm, thus changing from a light touch near neutral position to a large tonal change near the end of the arm stroke. In at least one embodiment, axis  58  of is substantially parallel to the string plane, or to the bridge. 
         [0023]    More generally, in  FIGS. 5A ,  5 B, and  5 C, a transport  57  biased in opposition to tension of strings  4  by spring means  53  pivots on an axis  58  relative to a base  25 . As shown in  FIGS. 5B and 5C , at least a portion of dive cam surface  52  is configured to engage follower  54  in alignment with a force vector  52   a  generating a torque about axis transport axis  58  in opposition to the desired direction of rotation of the transport about the axis, and in opposition to the torque of the lever  16 . 
         [0024]    In such a configuration, and in other configurations, the cam and follower (regardless of whether they act as a bias stop) act to limit the rotation of the arm in a way that shortens its stroke and reduces its purchase, while enabling a greater rotation of the transport device than would be possible even if the arm were locked to the transport. Such contact between cam and follower enables the transport to rotate through a greater angle than the arm itself. 
         [0025]    In the example, the movable tailpiece member  8  is urged by string tension to engage a bend cam follower  46  with a bend cam  51 . A bias limiter comprising a dive cam  52  and follower  54  may optionally employ a fixed stop  125 , for example in addition to or in lieu of a constant radius dive cam surface to oppose bias spring force at rest or during a bend. Similarly a fixed stop may supplement the bend cam and follower. Dive cam follower  54  preferably rotates about an axis fixed relative to a base, for example base  25 . 
         [0026]    In the example, the movable tailpiece member  8  pivots about axis  1   a  relative to base  25  during a dive, and pivots about bend axis  1   b  relative to biased transport  57  during a bend. (presuming engagement of a zero-slope dive cam surface during a bend, and a of zero-slope bend cam surface during a dive) In alternative embodiments, either of said bend and dive axes  1   a  and  1   b  are associated with a biasing transport, or a base, or another moveable member. 
         [0027]    It should be noted that at least one embodiment includes the dive cam so described, without association with the bend apparatus of the figure. 
         [0028]    Alternatively separate arms (preferably extending oppositely) may be provided for dive and bend cams, for example the cam surfaces of  FIG. 5A . Said cam axes are preferably not concentric, and said axes are preferably parallel to the bridge. 
       Flex Compensation 
       [0029]    The performance of any transposing vibrato device will suffer during excursions over multiple tonal steps on a low-modulus instrument, because the effects of neck deflection are non-linear with respect to changes in string tension. An embodiment of the present invention compensates for neck flex and other nonlinear displacements by moving use of two moveable tailpieces members engaging a common set of strings, the first configured to change string pitch in a harmonic manner, the other to alter string pitch in a more uniform or non-harmonic manner. 
         [0030]    A compensator associates motion of one tailpiece member with the other and the compensator is preferably adjustable in a manner so that the combined displacements of the two tailpiece members may be characterized to compensate for the deflection of the instrument. 
         [0031]    In a preferred embodiments, one of the tailpiece members moves relative to the other, for example a harmonic tailpiece member moveable relative to a base comprising a standard tailpiece member, where the standard member, pivots relative to the instrument. 
         [0032]    Compensation means, in the form of a cam, wedge, crank, screw, or other means preferably translates motion of moving component associated with the harmonic tailpiece member to motion of a non-harmonic tailpiece member. 
         [0033]    If the compensator comprises cam means, an adjuster or adjusters preferably enable reshaping the cam and/or repositioning the cam or cam follower 
       Simulated Dual Axis Operation 
       [0034]    Still another alternative embodiment of the invention simulates dual axis control by extending the control arm from pivot means having a pivot axis substantially parallel to the strings. 
         [0035]    Rotation of said arm toward the strings engages the vibrato device through suitable mechanical means to generate a bend effect, while rotation away from said strings and toward instrument body generates a dive effect. Said device preferably includes one or more biasing means to provide a free floating or a stable floating effect about the neutral position. 
         [0036]      FIGS. 1A and 1B  illustrate an example where the pivot means is a shaft  113   a  rotating on axis  113 , preferably substantially below and parallel to the strings. An arm  16 , preferably curved to provide suitable neck and body clearance, radiates from said shaft, having a handle  16   c , also preferably parallel the strings  4 . 
         [0037]    The shaft engages the vibrato unit by suitable means, for example by a connecting rod  42  pivoting on crank arm  16   a  extending from the shaft  113   a , and attached to a moveable member  8 , as illustrated in  FIG. 1A . 
         [0038]    The device may utilize any biasing means, e.g. simple bias springs (not shown) connecting the rotating member  8  or a crank from shaft  113   a  to the instrument body  25 . 
         [0039]    In the example shown in  FIG. 1A , the biasing means for the vibrato rotating member  8  is provided by return spring  56  pressing cam follower  55 . 9  toward cam  55 , also rigidly attached to shaft  113   a . The angle of contact of the cam with the follower is preferably adapted generate forces opposes to the string tension Preferably a slight change in angular contact at the neutral position provides tuning stablity when the return spring  56  is properly adjusted, as previously disclosed. 
         [0040]    The camfollower  55 . 9  rotates on a shuttle  56   a  (or alternatively a rocker) providing stable contact between cam  55  and cam follower  55 . 9  by confining the cam follower to a linear or arcuate path, and resisting unwanted tangential motion of cam follower about the cam. 
         [0041]    The actuation arm  16   c , substantially parallel to the strings in  FIGS. 1A and 1B  may alternatively have the shape of a cylindrical control surface (not shown), preferably coaxial with shaft  113   a , and of sufficient radius and surface friction to enable a rolling action with the palm side of the fingers while playing. 
         [0042]    In examples of alternative embodiments, the combination of arm  16 , shaft  113   a , and handle  16   c , take the form of a full or partial drum surface as in  FIG. 1C , or a contoured or substantially planar surface (for example a pickguard) hinged along an axis substantially parallel to the strings, as in  FIG. 1D . 
         [0043]    In alternative embodiments, the biasing means includes a cam and follower, at least one of which is moveable relative to a base, where rotation of the arm  16  is associated with relative motion of said cam and cam follower, such that rotating the arm  16  in one direction (preferably downward, away from the strings) alters the bias position of the main member  8  in a direction of increased bias spring force, for example similarly to the device described with respect to  FIG. 9C . Shaft  113   a  may connect directly or indirectly to said one or more cam, and may be configured to bend or swivel or link to intermittent arm or shaft means. 
       Mutes 
       [0044]    A preferred stringed instrument configuration includes a volume or muting control having a preferably cylindrical control surface moveable in a direction substantially tangential to an axis substantially parallel to the strings, for example a finger wheel  263  as shown in  FIG. 1B . 
         [0045]    This surface is associated (preferably by a shaft  262 ) with an electronic sensor  260  (preferably a potentiometer) wired, for example as a volume control, or as a separate muting (or gain) control, with the control surface immediately adjacent the strings, and with shaft axis substantially parallel to the strings. 
         [0046]    Typically the volume control on an electric guitar comprises a potentiometer of high resistance relative to the pickups, wired as a shunt parallel the pickups. The main volume control pot is sometimes used as a mute by dragging the edge of the small finger against a knurled knob. A present embodiment improves control by exposing a preferably cylindrical surface  263  to the inner surface of the fingers as shown. This pot may be used as the main volume control pot, or it may be a separate dedicated muting pot, preferably parallel to the first. 
         [0047]    An embodiment of a pot suitable for mutes and swells is illustrated in  FIG. 1B , and preferably includes a return spring  261  or a detent (not shown) associated with shaft  262 , returning the pot preferably to a high shunt impedance after use, or preventing inadvertent rotation. The spring is preferably of a non magnetic material to prevent interference with magnetic pickups. Alternatively, the shaft  262  between the finger wheel  263  and the pot  260  is long enough to effectively isolate the spring from the pickups, as illustrated. The muting pot preferably generates essentially infinite resistance at rest (when used for muting) and may preferably be rotated to drop to zero resistance. 
         [0048]    In one embodiment the muting pot may be switched (preferably by simple electrical switch means) from a muting function to a controller function as described with regard to an electronic vibrato arm. The device may alternatively be adapted to control other functions or effects without regard to muting. 
         [0049]    In another embodiment a device (such as a pot) connected to a single wheel when rotated one direction serves one function (such as muting), and when the wheel is rotated in the opposite direction from neutral the same device or a separate device connected to the same wheel serves a second function (such as control of an internal or external effects controller by connection thereto) 
         [0050]    In another embodiment multiple control surfaces (for example wheels or paddles) rotating on concentric or parallel shafts connect to separate (preferably resistive) devices to control multiple functions. An embodiment includes a separate return spring associated with each of one or more wheels or paddles. 
         [0051]    Connection to an external effects controller is, for example, by any of the means described with regard to an electronic vibrato arm sensor. 
         [0052]    The at rest resistance of a resistive device used to control an external device is preferable switchable (for example by reversing the connections on a pot to change the direction of operation) and configurable (for example by connection to a parallel characterizing pot to adjust the rate or range of operation.) In another embodiment any of multiple resistive devices associated with the same control surface are switchably interchangeable in a common circuit. 
         [0053]    The body ( FIG. 1B ) preferably has sufficient open area to allow clearance for manipulating the control arm  16  or control surface  263 , or both. To enhance the open area in an embodiment shown in  FIG. 1E , a cantilever knee rest  16   k  of high strength material, for example steel or composite, is fastened to a body of a generally weaker material (e.g. wood) by suitable means, for example wood screws or adhesive resin. In alternative embodiments a reinforcing material is molded into or attached to a body having a cantilevered knee rest portion. 
         [0054]    It should be understood that in at least one embodiment, either of the shafts  113   a  or  262 , or the actuator drum  263  of  FIG. 1B  engages an electronic sensor (for example a potentiometer) configured to or switchable to provide a (preferably resistance) signal to an effects processor for the pu. 
         [0055]    Flex Notes 
         [0056]    While the preferred embodiment comprises a harmonic vibrato tailpiece rotating relative to a substantially standard vibrato tailpiece, in order to simply and economically take advantage of the elevation of the strings during a dive, any separately movable tailpiece component, movement of which causes substantially uniform changes to the stretch of the strings, may, when combined with a harmonic vibrato device be used for flex compensation if actuated at the proper rate. 
         [0057]    For example the string anchors  10  may be mounted to a flex compensation base which in turn moves relative to harmonic main rotating member  8 . 
         [0058]    Or, for example, the string bearings  3  may be mounted to a base  69 , with base  69  and rotating member  8  both rotating about a common sub base  75 . 
         [0059]    Any combination of components substantially equivalent to the combination of a standard vibrato tailpiece and a harmonic vibrato tailpiece may be used to create a flex compensated harmonic vibrato device. (A tailpiece may be redirecting, and need not have its own anchors) 
         [0060]    The compensated device preferably includes machinery to elevate the bridge during a dive, to reduce string buzz. In the preferred embodiment, the bridge elevation machinery is associated with the flex compensation machinery, as disclosed elsewhere in this document. 
         [0061]    Flex compensation as disclosed here and as illustrated in the figures comprises an operatively associated combination of devices for simultaneous harmonic displacement and substantially uniform displacement of multiple engaged strings. Each of the two displacement devices engages a common set of strings directly or indirectly, and displaces the string in the region of engagement so as to change the elongation and tension of the string. 
         [0062]    Each of the harmonic and uniform devices preferably displaces strings by rotation of anchors or guides about an axis. 
         [0063]    The two devices may be articulated, so that one pivots relative to the other, or they may be separately connected to a base or instrument body. 
         [0064]      FIGS. 4A ,  4 B, and  4 C illustrate basic elements of flex compensation in examples where the pieces are not articulated. 
         [0065]    The string anchors may be, for example, on a standard vibrato tailpiece, a harmonic vibrato tailpiece, a base, a separate fixed tailpiece, or the instrument body. 
         [0066]    (The substantially uniform displacement device may provide separately adjusted or fixed nonuniformity of displacement to compensate separately for slight variations in string modulus, for example by providing guides or anchors adjustably positioned relative to a pivot axis) 
         [0067]    The combination involves associating the motion of a characteristic moving harmonic displacement member  401  (for example a rotating tailpiece, control arm shaft, or transposing hub) with the motion of a substantially uniformly displacing member  400  by way of compensation machine  402 . 
         [0068]    The compensation machine  402  is preferably or adjustably characterized to match the motion of the harmonic and uniform devices in such a manner that for any string displacement by the harmonic member  401 , the string displacement by the uniform member  400  will substantially cancel the string displacement due to instrument deflection under varying string tension. 
         [0069]    Compensation machine  402  (which may include any characterizable machine or combination of machines, for example a flexibly adjustable cam, an eccentric, a crank, a rocker, a lever having adjustable length and engagement delay, or a screw) is shown in  FIG. 4A  as a black box engaged by a rotating harmonic tailpiece  401  (via engagement means  404 ) to make a slight adjustment to the uniformly displacing member  400  (via engagement means  403 ). 
         [0070]    Some or all of the compensation machinery may be inherently incorporated into one or both of the string displacement devices. 
         [0071]    In  FIG. 4C , for example, the machine may comprise string-bearing idler sheaves  406  mounted eccentrically relative to a shaft or journal, where the degree of eccentricity and at-rest angle of engagement with the strings are preferably separately adjustable. The shaft may be activated for example directly by the control arm  401   a , and output from the machine may be directed to the harmonic tailpiece  401   b . The eccentric assembly itself may be considered both part of the uniform tailpiece  400  and the compensation machine  402 . In the example of the figure, the eccentricity of shaft  400   s  is adjustable within a slotted hub  400   h , rotating in journal support  400   j , preferably fixed relative to base  69  or body  25 , as are string anchors  10 . Uniform displacing member  400  may share a common bias spring with harmonic tailpiece  401   b.    
         [0072]    In unshown examples, the sheaves  406  may be replaced by cam or cams engaging the strings or separate moveably tailpiece(s). The anchor  10  may alternatively be fixed relative to said cams or said shaft, and the cams may for example be pressed into sheet stock pivoting on a knife edge fulcrum. 
         [0073]    For simpler use of cams in compensation machine  402 , in a preferred configuration, bias spring means  405  preferably opposing string tension, urge the uniform tailpiece in a direction limited by compensation machine  402 . In this configuration, the radius of a cam follower is less likely to interfere with the cam dimensionally. However, machine  402  may exert force in either direction, and no bias spring is required. 
         [0074]    Machine  402  and bias spring means  405  are preferably configured to engage base  69  or body  25 , as shown. But may alternately engage an intermediate base as previously described or a moving component as a reference structure. 
         [0075]    It should be noted that at least one embodiment comprises separate devices for flex compensation in each of the bend and dive directions, either or both of which is adjustable. 
         [0076]    It should be noted that at least one embodiment comprises in combination a moveable member, motion of which causes a harmonic change in string pitch of at least two strings, an another moveable member, motion of which causes a substantially non harmonic change in string tension, said members mechanically associated with each other such that motion of one causes motion of the other, where the degree of association is configured or configurable to compensate for flexibility of the instrument to which the device is attached. 
         [0000]    Transport Separate from Device 
         [0077]    It should be noted that any part or all of the control arm and transport combination may be mounted apart from the other components of the device and connected by linkage above, below, or through the body of the instrument. 
         [0078]    For example, mounting the control arm pivot axes farther toward the tuning head allows good tactile response due to the improved angular purchase, while avoiding clutter on the face of the body. 
       Hidden Mechanism. 
       [0079]    It should further be noted that the disclosed device may be fabricated with any part or all of the actuation mechanism concealed within the instrument (or for example, below a pick guard), including control arm pivot, transport means, and transposing means, and associated springs. 
         [0080]    Said device may be implemented as a retrofit unit or built into an instrument. Said instrument body may act as the base or sub-base previously described. 
         [0081]    In particular, the control arm shaft or shaft extension may extend below the hub or a cam or rocker may be extended from the control arm hub through the base to engage the spring block below the face. 
       Cantilevered Guide 
       [0082]    In  FIGS. 2A through 2J , for one or more strings an adjuster (preferably a screw  15  in a lower block  8   b  of main rotating member  8 ) is used to push guide  6  on the end of guide extender  6   x  away from main pivot axis  1 . Guide extender is preferably a column extending through a preferably slotted base plate plate  8   t  (in  FIGS. 2A ,  2 B,  2 D, and  2 E), where the slots  12  are preferably sized to prevent passage of lower end of extender  6   x  when unstrung. 
         [0083]    Shape of front edge (toward bridge) of extender  6   x  and location of front edge  8   e  of slot  12  are preferably matched to position guide  6  along a suitable arcuate path  7 . Extender may be straight, as shown in  FIG. 2C  or curved as in  FIG. 2A .  FIG. 2C  also shows an alternative embodiment where guide extender  6   x  comprises bulbous adjuster screw  15  engaging preferably flat or convex threads in at least one side wall of the socket, allowing column to tilt as it extends, with the upper end resting against the top lip of a socket. Side wall threads are preferably provided by a threaded rod inserted into an adjoining socket. 
         [0084]    In a preferred configuration, side walls of a slot for an individual guide column  6   x  are provided by parallel packing of adjacent guide columns into position. 
         [0085]    In the examples of  FIGS. 2C and 2D , guides  6  are preferably pivotingly cantilevered from a cantilevered column  6   x  to resist string tension. The column in the 2 examples preferably comprises a threaded shaft with straight cylindrical or contoured surface. 
         [0086]    In  FIG. 2D , a transverse rotatable cylinder  15   a  rotates about a fixed axis in block  8   b , being threaded to adjuster screw  15  on the end of guide extender  6   x.    
         [0087]    In  FIG. 2E  column  6   x  may be turned to shape (for example on a screw machine) with internal string path and anchor  10 , with swiveling ball and socket connection on adjuster screw  15  to resist axial motion of the column, and preferably with machined flats on the sides to resist rotation in slots  12 . 
         [0088]      FIG. 2F  shows a string anchor (for example a ball cup) suspended in tension, and pivotable about 2 axes relative to a cantilevered guide support column, for example suitable for connection to a cantilevered column modified from those shown in  FIG. 2C ,  2 D, or  2 E. Connection in the example is by a countersunk knife edge riding in a turned groove. 
         [0089]      FIG. 2G  shows a string anchor (for example a ball cup) suspended in tension, and pivotable about 1 axis, preferably centered on arcuat guide path  7 , for example suitable for application to a cantilevered column modified from one shown in  FIG. 2A ,  2 B, or  2 E. In a preferred configuration, pivoting anchor  10  has includes a tail  10   t  enabling balancing of the anchor by finger pressure during loading. A ball cup or string slot may be in either end of the extended anchor. 
         [0090]    In  FIGS. 2F and 2G  the guide position adjuster  15  preferably includes retaining means (for example a ball socket in a setscrew in  FIG. 2G ) to prevent motion of the column in either axial direction from the adjusted position. 
         [0091]    Similarly (for example in  FIG. 2H ) an anchor (for example a combined fine tuner  10   d  and string clamp  10   c , adjustable by setscrews  10   a  and  10   b ) may be attached to one or more guide columns. The fine tuner preferably pivots about the focus of a preferably cylindrical guide  6 . String engaging surface of guide  6  may be fixed relative to the cantilevered column, or it may comprise a revolving sheave. Column adjuster  15  includes means to prevent axial motion of the column, for example a ball retainer as shown, or for example dual opposed setscrews, not shown. 
         [0092]    In  FIGS. 2A ,  2 B, and  2 G, keying means between guide column  6   x  and rotating member  8 , for example parallel slots in top plate  8   t  shaped to fit columns  6   x  having rectangular cross section, preferably substantially resist rotation of column  6   x  about its longitudinal axis. 
         [0093]    In Fix  2 A through  2 H, cam follower means, for example, top plate edge  8   e  positions the cam face of cantilevered guide support column  6   x . Alternative follower embodiments comprise roller or shaft means Preferably a flange  8   f  extends from the block  8   b  or the top plate  8   t  to support pivot means for the tailpiece  8  to rotate about main axis  1 . A flange  8   f , for example, comprises a journal hole, a cantilevered shafts, or a knife edge fulcrum component positioned to enable pivoting of main member  8  about main axis  1  (pivot means not visible) 
         [0094]    In the embodiments of  FIGS. 2F ,  2 G, and  2 J, string guide  6  is a pivot for a string anchor, so that the tension of the string acts to align the string with the guide pivot axis  6   p.    
         [0095]    The guide axis itself is preferably adjustable along an arcuate path  7  substantially as previously described in the present text or the parents, where the string axis intersects the guide axis at a defined angle relative to a ray from main axis  1 , about which first member  8  rotates. 
         [0096]      FIG. 2J  illustrates an example of an anchor fixture  10   f  pivoting freely on guide  6  about guide pivot axis  6   p . The fixture is preferably associated with a guide surface  6   s  (preferably a smooth convex shape or a roller) configured to engage the string  4  between the string bearing  3  (a bridge saddle in the example) and the string anchor  10 , preferably with string  4  wrapping slightly about guide surface  6   s . The string tension urges surface  6   s  angularly about axis  6   p  in opposition to the urging of string anchor about axis  6   p , thus urging alignment of string  4  with guide pivot axis  6   p.    
         [0097]    In and example shown in  FIG. 2J , anchor fixture  10   f  is associated with a fine tuner. A fine tuner associated with an anchor fixture may take any suitable form. In the example, the fine tuner is a lever  10   d  pivotable relative to fixture  10   f  and comprising an adjuster  10   a . In the example, the fine tuner lever  10   d  supports a string anchor  10 , illustrated, for example, as a ball cup. 
         [0098]    In an alternative embodiment anchor  10  further comprises a string clamp, for example as illustrated in  FIG. 10H . In an alternative embodiment, a fine tuner engages a string between guide surface  6   s  and anchor  10 . In another embodiment, the fine tuner adjusts the position of guide surface relative to the anchor fixed relative to an anchor fixture. In another embodiment, an anchor fixture comprises a guide surface and an anchor with no fine tuning adjuster. 
         [0099]    In the configurations of  FIG. 2F ,  2 G, or  2 J pushing either direction on an individual anchor  10  or anchor fixture  10   f  (directly or with a lever extended for that purpose, for example a palm lever) enables bending an individual string to a higher pitch. In one embodiment, a bend limiter, for example limit screw  10   x , in  FIG. 2J , allows bending a string a desired interval by rotating fixture  10   f  in one direction, while allowing greater rotation in the opposite direction. Configured as shown, rotating fixture  10   f  beyond its limit causes rotation of the entire main member  8 . Additional improvements not shown in the figure are a separate lever to improve the mechanical advantage or rotating the fixture towards its limit, to reduce the urge toward premature chord bend during an individual string bend, and compensation to effective guide radius from main axis  1 , during a string bend. 
         [0100]    In the discussion of all  FIG. 2 , it is understood that main rotating member  8  describes the combination of all of members  8   b ,  8   e ,  8   t ,  8   m , and  8   f  that exist in that figure. 
         [0101]    In at least one embodiment of devices illustrated (for example  FIG. 2G ) moveable member  8  is fabricated from a stack of sections (for example a top plate  8   t , a bottom block  8   b , and a middle block  8   m ) fastened together preferably by tie rods or screws (not shown). Any of the 3 sections may be fabricated by any one or combination of, for example, extrusion, cutting, drilling, boring, milling, broaching, and tapping. In a simple embodiment a lower section  8   b  is extruded having only round holes, some of which are tapped to receive an adjusting screws  15 . Others (for example string anchor holes or  FIG. 2A ) are preferably counterbored with a tapered shoulder to reduce stress on ball end lashing. Other extruded holes enable tierods or. An embodiment of the middle section is preferably a slotted extrusion, or an extrusion of slots and string holes, or it may comprise multiple simple standoff means between upper and lower sections. In one embodiment the upper section is a slotted plate, but in another it is a continuation of the slotted extrusion, machined to include pivot means (for example bearing shaft bores) centered at main axis  1 , for pivotably engaging base  69 . 
         [0102]      FIG. 2B  illustrates an alternative embodiment where flanges  8   f , bottom plate  8   b , middle plate  8   m , and top plate  8   t  are cut and formed preferably from a single sheet of metal, preferably by simple stamping operation. The configuration preferable comprises at least one stiffener  8   s  (preferably a standoff between top plate  8   t  and bottom plate  8   p ), and adjuster bosses  15   b , fastened to the formed plate, for example, by pressing, welding, peening, or screwing. Bosses  15   b  are preferably fabricated by screw machine. In alternative embodiments boss  15   b  is formed and threaded into base plate  8   b , or adjusting screws  15  threaded directly through a flat bottom plate  8   b.    
         [0103]    The discussion of  FIGS. 2A through 2J  has centered on features related to rotating member  8  and string guides  6 . Other optional or necessary components to a device are not shown in the figures. 
       Bend Limiter 
       [0104]    In the embodiments of  FIGS. 3A and 3C  a separately biased guide crank  220  is provided for at least one sting. It preferably rotates on a common axis  1  with main rotating member  8 , and rests against a stop  222  relative to main member  8 . As main member  8  rotates in a bend direction, guide crank  220  rotates with it under the force of separate bias spring  122 , until preferably adjustable (by an adjusting screw, for example) stop  221  engages base  8 . In the example, crank  220  comprises string anchor means  10 , for example a slot positioned to enable string  4  to wrap over the surface of guide  6 . In a preferred embodiment, a quickly changeable adjuster, for example a sloped or stepped axial cam  221   a  in  FIG. 3A  between stop  221  and base  69  (pivotable about an axis  221   x ), enables a user to quickly select from among 2 or more bend limits during a performance. The range of adjuster  221   a  preferably is sufficient to enable adjusting the limit to totally prevent bend (sharpening) motion of crank  220  relative to base  69 . Adjuster  221   a  preferably comprises knob or lever means as shown to enable quick adjustment. 
         [0105]    The separate crank  220  preferably includes string anchor means separate from the main member, for example a slot for receiving the ball end of a string, as shown, preferably far enough from the guide  6  to isolate the guide from the stiffness of ball end lashing. Main member may optionally be partially biased by separate balancing spring  40 . 
         [0106]    The radius of guide  6  from axis  1  may be adjustable, for example by set screws on a flexible guide bracket  220 , as illustrated in  FIG. 3C , or it may be fixed, for example as illustrated in  FIG. 3A . A single fixed guide permits all other guides to be adjusted relative to the fixed guide to accomplish tuning of the device. Actuation effort may be adjusted by modifying the purchase of the actuator mechanism between the control arm and main member (not shown). 
         [0107]    In  FIG. 3B  one or more guide means may be equipped with locking slide means, for example a string anchor  225  adapted to slide through or around a modified guide  224  and biased by string tension against a stop  223 . Locking means, for example a thumbwheel  226  (or cam, lever, or latch), associates modified guide  224  with sliding anchor when desired. In one embodiment thumbwheel  226  is threaded onto a threaded shaft  226   a  through cylinder rotating within a guide cavity, with anchor means  225  extending through the cylinder and the threaded shaft. Tightening said thumbwheel pulls anchor against interior of cylinder. When disengaged rotation of main member  8  has no discernible effect on pitch of the disengaged string. 
       Electronic Vibrato 
       [0108]    An electronic embodiment of control means, as discussed in a parent application, provides an arm rotatable about one or two axes, with rotation resisted by spring means and a force or position sensor measuring rotation about at least one axis. Sensors previously illustrated may be of any type, for example piezoelectric, strain gage, potentiometer, inductive, magnetic, or capacitive sensors, and may generate analog voltage, analog current, digital, or frequency signals when connected to a suitable power source, or simple resistance values. In a preferred embodiment, an arm is configured to attach to a standard vibrato device, and rotation about an axis parallel to the strings actuates a sensor, for example a potentiometer, configured to be connected to an external processor. 
       Clarifications Notes: 
       [0109]    Not all embodiments of the disclosed invention are are described here. 
         [0110]    It is understood that a device configured to accept modification to include elements described here falls within the scope of this disclosure, as do elements configured to be added to a device such that the modified device falls contains disclosed elements. 
         [0111]    It is understood that, where applicable, flex compensation may be added to an embodiment for which it is not illustrated, and that one embodiment of flex compensation may be substituted for any other. 
         [0112]    It is understood that, where applicable, a bend or dive latch may be added to an embodiment for which it is not illustrated, and that one embodiment of a latch may be substituted for any other. 
         [0113]    Stated position or orientation of an axis, journal, or shaft, unless otherwise stated, generally refers to orientation at-rest or at neutral position, where the axis may be associated with a moveable component, the movement of which would change the orientation of the axis, journal, or shaft. 
         [0114]    Pivot or rotation means may include flexible solid connection approximating the functionality of a pivot, where practical. 
         [0115]    In a description including an instrument body, it is understood where practical, that a separate discrete base fixed or moveable relative to the body may be substituted to fill the function of the body in an alternative embodiment. Likewise a body may be substituted for a base in alternative embodiments. 
         [0116]    It is understood that, where practical, for any disclosure of a device having a control arm rotating relative to a discrete moveable transport device, an alternative embodiment includes a control arm rotating about two axes on a hub in hub retainer, where one of two pivot axes rotates relative to a hub retainer. 
         [0117]    Use of common terms of the trade, for example “tone block” is meant to aid in identifying a component in a drawing, and not necessarily for describing or limiting its function in the present disclosure. 
         [0118]    Where bias springs shown parallel to the strings, it is understood, where practical, that an alternative embodiment of the disclosure includes bias means at any angle, including normal to the string direction. 
         [0119]    It is understood that any device configured to be combined with another device so that the combination yields a device equivalent to one or more elements of the present disclosure, also falls within the present disclosure. 
       Additional Notes 
       [0120]    Because the pitch of a string varies with the square root of the string stretch, and the scale of the invention is large, the invention is robust enough to allow significant deviation from optimal design without creating excessive transposing errors. Thus any configuration substantially equivalent to the preferred optimal configuration falls within the scope of the invention. The low angle of rotation allows strings to wrapped about geometrically wrong side of said guide or about a guide in a geometrically incorrect track without excessive harm to pitch accuracy. Guide means may be visually placed by measurement or by index marks included on the device, and a small error in placement will be undetected acoustically. 
         [0121]    An embodiment of the invention taking advantage of said tolerance in a flat plate configuration may use fewer than the total complement of arcuate paths. It may also use additional (for example parallel to the high e path) non converging paths to allow flexibility in setting up said device for multiple tuning. Where multiple paths converge near the main pivot axis, one may continue while the others terminate short of the convergence point. Alternatively, a less preferred configuration may employ a perforated plate straight slots approximating the preferred configuration. ( FIG. 15 ). Guides on straight or curved paths (on a flat plate tail piece, for example) may be configured to vary the angle from tangency among the strings to approximately compensate for neck flex. 
         [0122]    A control arm axis normal to the string plane as disclosed herein is additionally beneficial when applied to acoustic guitars, where motion of the control handle will not conflict with vibratory rotation of the sounding board about the bridge. 
         [0123]    Mechanical construction listed above is by way of example and conceptual schematic only. Any configuration functioning according to the described principles falls within the scope of this invention. In particular switching locations of cams and cam followers, rotating axes, and utilization of mechanical linkage in place of cams, or vice versa, falls under the scope of this invention. 
         [0124]    Size, shape and location of components shown was selected for clarity of illustration, and not to illustrate a preferred size or shape or location. Variations, which may be obvious to those skilled in the art, fall within the scope of this invention. 
         [0125]    Mounting locations and axes of control arm, cams, cam follower, transposing hub, or linkage may be interchanged, reversed, or inverted from that shown. 
         [0126]    In  FIGS. 21B-23D  where balancing spring  40  or harmonic dive bias spring  122  extending from rotating member  8  within the instrument body is shown anchored to base extension  119   b , it should generally be clear that said spring may alternatively be anchored to the base  68  or to the body  25  in lieu of or in addition to standard bias spring  123 . 
         [0127]    In an alternative embodiment to  FIG. 16H  of the parent, the fine tuner  10   d  shown may alternatively pivot about a guide  6 , as in figures 
         [0128]    Stops or other limiting devices may be relocated as desired. 
         [0129]    String bearing means may serve also as bridge saddle means. 
         [0130]    String guide means and string anchors may be combined into a single component or adjacent components, and ball cup anchor means may be pivotally suspended between guide means and bearing means. 
         [0131]    The “substantially arcuate” adjusting path of string guides on a flat plate embodiment may include linear slots tangential to an arc as shown in  FIG. 15 , or discrete holes arranged in a suitable pattern. 
         [0132]    Main rotating member pivot axis “substantially parallel” to the plane of the strings includes axes slightly oblique orientation to accommodate differences in crank length from lowE to highE. 
         [0133]    Spring anchors shown in some drawings as rigid pins are schematic representations, and actual embodiments may be expected to include adjustable claw, or other spring adjustment means. 
         [0134]    Bridge saddles preferably use grooved ball bearing saddles where the groove is preferably offset from the center of the bearing, as show in  FIG. 32B  thereby putting the balls in the ball race in a bind as shown in  FIG. 32C . This binding action prevents rattle without increasing friction 
         [0135]    The term “vibrato” used in this specification and claims is intended to include temporary increase or decrease in string pitch with or without oscillation. 
         [0136]    Where an activation mechanism is disclosed by way of illustration as it is applicable to a given vibrato device configuration, it should be understood that the invention is not limited to a vibrato of that style or rotating about that same axis, but includes any vibrato device configuration to which it applies. 
       Disclaimers 
       [0137]    Where numbered elements in a figure are not described in the discussion of that figure, their basic descriptions may generally be taken to be substantially similar to elements of the same number described previously, where appropriate, and where the description is essential for understanding of the figure. 
         [0138]    In most instances reference to a shaft element being oriented substantially normal to the string plane, for example, refers to the an angle at rest or neutral position, and encompasses any useable axis sufficiently askew to the standard vibrato fulcrum axis or the dive axis of the transport, for example, to allow rotation about one axis without interfering with rotation or stability about the other. 
         [0139]    Pivot post brackets my be configured to include a fixed or adjustable (for example eccentric) post positioned to provide alignment of the moveable tailpiece in a direction parallel to a vector constructed between the pivot posts. 
         [0140]    For figures related to electronic vibrato arm, it should be understood that at least one equivalent or alternative embodiment comprises a potentiometer as a rotation sensor. 
         [0141]    Any single element or combination of elements disclosed herein whether from the same or different embodiments, falls within the scope of this disclosure. One or more elements of this disclosure may be combined with any known art or obvious improvement to create an embodiment falling within the scope of this disclosure. 
         [0142]    It is to be understood that the illustrations, descriptions, and embodiments in this disclosure are by way of example only, and in no instance is any part of this disclosure intended to limit the scope of the disclosure or claims, regardless of the language used in the description. 
         [0143]    Some of the embodiments described herein contain multiple novel features. Limitations which may be illustrated in the figures or described in the text of the specification, are not intended to limit the scope of the disclosure of any embodiment or of any claim or the use of a particular element to a given embodiment. A device incorporating some but not all of the teachings of a given embodiment falls within the scope of this disclosure. Each novel element described herein may be claimed individually. A device incorporating elements from two or more disclosed embodiments falls within the scope of this disclosure. 
         [0144]    The location and orientation, of rotational axes, shafts, journals, cams and cam followers, transports, springs, and other disclosed mechanical components, and their association with other components of the devices disclosed are by way of example. It is understood that applying the teachings of this disclosure may involve change, interchange, reversal, or swapping of locations, orientations, and associations while maintaining the principles taught. 
         [0145]    Any of the various methods available to scale the stretch of each string during actuation of a vibrato device, for example to maintain relative pitch, may be referred to as a proportioner. 
         [0146]    A transport is preferably a mechanism allowing for displacement relative to a reference component of a first axis (associated with said transport) along or about a second axis, while resisting displacement of said first axis along or about other axes relative to said transport or relative to a reference component. 
         [0147]    Pivot means disclosed or illustrated are for schematic illustration only, and it is understood that any pivot mechanism meeting the requirements of the device may be used, including knife edged fulcrum and journal and shaft. It is to be understood that illustration of any one pivot device does not amount to a disclosure of a preference for that device in any particular embodiment, unless expressly stated. 
         [0148]    In every embodiment illustrated herein, it is understood that the type of springs and their attachment means and their location or orientation is by way of example only. Compressive springs, leaf springs, coil springs, torsion springs, or tensile springs may be used as may be appropriate. Where springs are illustrated without adjustment means, it is understood that any appropriate adjuster falls within the scope of the disclosure and claims. 
         [0149]    The slope of a radial cam is generally expressed as dr/da where r is radius and a is angle of rotation. It should be understood that the sign of slope is generally a function of force direction, and not radius or height. 
         [0150]    Device may be constructed of any solid material having adequate strength and rigidity. Polished plated steel is a preferred material for economical fabrication. Polished stainless steel is preferred material to eliminate a plating step in smaller lots. 
         [0151]    Instruments fitted with the disclosed devices and methods of retrofitting existing instruments with the disclosed elements also fall within the scope of the invention.