Abstract:
A musical instrument includes a soundboard, a bridge in contact with the soundboard, vibratable strings in contact with the bridge, a movable member disposed adjacent to the vibratable strings, a driving mechanism engaged with the movable member and configured to cause the movable member to move relative to the vibratable strings, and actuators. Each actuator is configured to displace, when actuated, an associated vibratable string such that the string is caused to come into contact with the movable member at a point of contact. Displacement of the string corresponds to movement within a first plane that is orthogonal to a second plane, the second plane being tangential to the movable member at the point of contact.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §119(e)(1) of U.S. Provisional Application No. 61/751,771, filed on Jan. 11, 2013, which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     This application relates to bowed stringed musical instruments. 
     BACKGROUND 
     Bowed stringed musical instruments are instruments that produce sound by the vibration of a string that has been brought into contact with a bowing surface. Typically, in such instruments, bowing occurs as a frictioned surface moves relative to a string that is anchored at one end to a bridge; the string vibrates, the string&#39;s vibrational energy is transferred via the bridge to a soundboard or other mechanical structure, and sound is produced as the soundboard resonates. 
     SUMMARY 
     This application describes a bowed stringed musical instrument that produces sound by bringing one or more vibratable strings into contact with a movable member, driven by a driving mechanism such as a rotating shaft and preferably coated with a high-friction substance such as rosin, whereby the resulting string vibrations are transferred to a soundboard by a bridge. In response, the soundboard resonates at frequencies within the range of the human auditory system to generate changes in acoustic pressure that the human ear detects and recognizes as sound. This sound generation mechanism is similar to stringed instruments such as the violin, where a rosined bow is drawn across one or more strings to generate string vibrations that are transferred to a resonant soundboard. The present instrument thus is capable of generating tones reminiscent of violin-like instruments. However, by employing a driving mechanism shaft to move a movable bowing surface—as opposed to a violin bow, for example, which is moved back and forth by the human arm—the instrument is capable of generating notes of indefinite sustain. Further, the strings can be brought into contact with this surface by any of a number of actuation mechanisms, such as piano-like keys, which operate as discrete note selectors. Each actuator displaces a corresponding string in a plane orthogonal to the plane tangent to the movable member at a point where the string will contact the surface. The resulting angle at which the string contacts the movable member helps achieve optimal transfer of any kinetic energy of the movable member to vibrational energy of the string. Further, by selecting notes by actuating these actuators, rather than by changing the length of a single vibrating string, as with a violin, the user can employ common piano and keyboard techniques to generate violin-like sounds. Further, by employing a greater number of fixed-length strings—as opposed to a lesser number of variable-length strings, as in a violin—the instrument may be made capable of generating complex harmonies that result from bowing many strings at once. 
     Certain implementations may provide other potential advantages. For example, one such advantage may be to improve the instrument&#39;s usability in diverse musical applications. One way this advantage may be achieved is by increasing the instrument&#39;s maximum attainable perceived sound volume relative to input kinetic energy. This improves the instrument&#39;s usability in band or orchestral settings, by making it better able to compete for volume with louder instruments, without the assistance of electrical amplification. It also improves the instrument&#39;s usability in recording settings, where the signal-to-noise ratio of the recorded instrument—a metric directly related to the sound quality of recorded music—increases with the instrument&#39;s natural acoustic volume. One way that certain implementations increase the maximum attainable perceived sound volume is by displacing a string such that as much of the moving surface&#39;s kinetic energy as possible is transferred to resultant vibrational energy of the string, which is related to the acoustic pressure, and thus the perceived sound volume, of the instrument. Another way is by encouraging a soundboard to resonate with maximum displacement, which helps translate more of a bowed string&#39;s vibrational energy to acoustic pressure, thereby increasing the perceived sound volume of the instrument. In some implementations, soundboard displacement is increased by employing a pivot post, coupled to the bridge at a single point of contact, such that vibration of a string causes the bridge to vibrate around the point of contact. 
     Another way that usability in diverse musical applications may be improved in certain implementations is by allowing the use of “drone” strings, which remain in contact with a moving surface without requiring actuation; these strings provide “pedal” tones which are highly characteristic of certain genres of music, such as the traditional music of Ireland, Scotland, and India. 
     Another way that usability in diverse musical applications may be improved in certain implementations is by enabling the use of dynamic acoustic effects, such as tremolo and phasing, and acoustic dampening effects. 
     Another way that usability in diverse musical applications may be improved in certain implementations is by converting string vibration to electrical signals, allowing the instrument to be interfaced with electrical amplification, electronic signal processing equipment, and recording equipment. This conversion may be performed, for example, by an electromagnetic pickup; a piezoelectric transducer; or a microphone. 
     Another way that usability in diverse musical applications may be improved in certain implementations is by allowing actuators to be controlled by Musical Instrument Digital Interface (MIDI) signals. For example, a MIDI signal could encode pitch and note velocity information and direct the strings of the instrument to produce notes of the encoded pitch and velocity. 
     Another potential advantage is improving ease of operation by musicians of various backgrounds and skill levels. For example, certain implementations help ensure uniformity of sound volume across all strings of the instrument by displacing strings toward a moving surface such that all strings contact the surface at the same angle. The instrument is made easier to operate because the operator can rely on all strings being bowed with roughly consistent amplitude, thus producing roughly consistent sound volume across strings—a desirable characteristic of stringed instruments—without the need for the operator to manually compensate for differences in volume across strings. 
     As another example, certain implementations feature a linear array of actuators, such as keys. This may improve ease of operation because musicians skilled with common instruments featuring linear keyboards, such as pianos or accordions, can transfer their skills directly to the presently described instrument. 
     Certain implementations also connect such actuators to strings via a cable linkage system, which helps allow the linear keyboard, which improves the instrument&#39;s ease of operation, to coexist with the orthogonal string displacement, which improves the instrument&#39;s usability in diverse musical applications. 
     Another potential advantage is ease of manufacturing, which results in a lower cost of manufacture. This advantage may be provided, for example, by implementations with a tubular soundboard, because it is easier for a manufacturer to attach a radial bridge (as might be used in bowed stringed musical instruments that employ a wheel) to a tubular soundboard than to a flat soundboard. This advantage may also be provided, for example, by implementations that have a radial keyboard, with actuators spaced around a curved surface, because the uniformity of the distance and positioning of each key relative to its respective string allows for an identical action for every note throughout the keyboard, which makes the instrument easier to manufacture. 
     Another potential advantage is compactness of the instrument, which assists portability and better enables the instrument to be used in small venues. This may be provided, for example, by implementations that have a radial keyboard, with actuators spaced around a curved surface. Radial keyboards take up less linear space than a linear keyboard with the same number and size of keys. This advantage may also be provided by implementations with a string tension adjustment mechanism, which increases the number of playable notes without increasing the number of strings required. 
     Another potential advantage is ease of user adjustment and calibration, which reduces the time and effort a manufacturer must spend to provide user support. This advantage may be provided, for example, by implementations that have a bridge coupled to a user-adjustable pivot post, because the user-adjustable pivot post allows the user to calibrate the bridge-and-soundboard system (and help achieve optimal acoustics) without disassembling the instrument, which presumably would require the assistance of the manufacturer. 
     Another potential advantage is consistency of volume among notes, which is a generally desirable characteristic of stringed instruments. This advantage may be provided for example by implementations that drive the moving surface with a motor, because motors can provide a more consistent rotational velocity and thus a more consistent bowing amplitude than can, for example, a human-powered moving surface. 
     Another potential advantage is energy efficiency, which may be provided for example by implementations that feature a human-powered moving surface, because this eliminates the need to power the moving surface with an external energy source, such as fuel or electricity. 
     Other aspects, features, and potential advantages will be apparent from the following figures and detailed description. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1A  shows a perspective view of a musical instrument. 
         FIG. 1B  shows a side view of a musical instrument. 
         FIG. 1C  shows a front view of a musical instrument. 
         FIG. 2  shows a perspective diagram illustrating string displacement orthogonal to a movable member. 
         FIG. 2A  shows a schematic diagram illustrating string displacement orthogonal to a movable member. 
         FIG. 2B  shows a perspective photo illustrating string displacement orthogonal to a movable member. 
         FIG. 3  shows a rotating shaft and attached movable member. 
         FIG. 4  shows key actuators arranged linearly. 
         FIG. 5  shows key actuators arranged radially. 
         FIG. 6  shows a cable linkage system connecting actuators to strings. 
         FIGS. 7A ,  7 B,  7 C, and  7 D show a pivoting bridge mechanism. 
         FIG. 8  shows a flat soundboard. 
         FIG. 9  shows a tubular soundboard. 
         FIG. 10  shows a driving mechanism driven by a motor. 
         FIG. 11  shows a motor speed controller system. 
         FIG. 12  shows a driving mechanism driven by a foot-powered treadle system. 
         FIG. 13  shows three possible means of electronic transduction: electromagnetic pickup; piezoelectric transducer; and microphone. 
         FIG. 14  shows solenoids used as string actuators and controlled via a MIDI system. 
         FIG. 15  shows a string dampening mechanism. 
         FIG. 16  shows a trill mechanism and a vibrato mechanism, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1A ,  1 B, and  1 C, a driving mechanism  10  causes movement of movable member  20 , disposed adjacent to a plurality of vibratable strings  30 . A plurality of actuators  100 , each actuator corresponding to an associated vibratable string  30 , is configured to displace vibratable strings  30  such that said strings come into contact with movable member  20  at at least one point of contact. Movable member  20  has a coefficient of friction such that when movable member  20  is in motion and is brought into contact with vibratable strings  30 , kinetic energy of the movable member  20  is transferred to vibrational energy of the vibratable strings  30 . Vibratable strings  30  are stretched between two end plates  40  and anchored at one end by tuning pins  50 . Vibratable strings  30  are coupled to a bridge  60  by bridge pins  70  that are spaced around the bridge  60 . Bridge  60  is coupled to a soundboard  80  via bridge feet  90 , such that vibrational energy of the vibratable strings  30  is transferred via the bridge  60  to vibrational energy of the soundboard  80 . This vibrational energy causes the soundboard  80  to resonate at frequencies within the range of human hearing, creating changes in acoustic pressure that the human ear perceives as sound. 
     Referring to  FIG. 2 , for each of the vibratable strings  30 , a corresponding member of actuators  100 , when actuated, displaces the vibratable string  30  in a plane perpendicular to the plane tangent to the movable member  20  at a point where the vibratable string  30  contacts the movable member  20 .  FIG. 2A  shows the front view of an implementation in which the driving mechanism  10  is a single rotating shaft, and movable member  20  is a single cylinder that rotates with said shaft. The wheel and shaft rotate around an axis directed into the page. Arrows  120  show the vectors along which each vibratable string  30  is displaced; each such vector is perpendicular to the plane tangent to the movable member  20  at the point where vibratable string  30  contacts the movable member  20 . Arrows  130  show the vectors along which the vibratable string  30  vibrates when contacting the movable member  20 ; each vector is in said plane.  FIG. 2B  shows a perspective view of one such implementation. Movable member  20  need not be cylindrical, or entirely curved; in some implementations, movable member  20  comprises a belt that is driven by a driving mechanism  10  that rotates two or more shafts, around which the belt is displaced. 
     In a particular implementation, pictured in  FIG. 3 , driving mechanism  10  is a single shaft that rotates a wheel, with radius approximately sixteen inches, whose movable outer surface  20  is coated in a high-friction material, such as rosin. Bridge  60  comprises a curved outer surface whose curvature approximates the curvature of the movable member  20 , and to which a plurality of vibratable strings  30  is attached. The tension of each vibratable string  30  is adjusted, preferably by tuning pins  50 , such that bowing the vibratable string  30  plays a note in the chromatic scale, and that bowing adjacent strings  30  results in playing adjacent notes in the chromatic scale. Sixty-one vibratable strings  30  may be used to allow a pitch range of five octaves. More vibratable strings  30  may be used if a greater chromatic range is desired. Fewer vibratable strings  30  may be used if wider string spacing is desired, or if a smaller movable member  20  is desired. 
     In some implementations, such as shown in  FIG. 4 , each actuator  100  is a key such as those found in a piano. In a particular implementation, shown in  FIG. 4 , the keys are arranged in a straight line, as in a piano, helping musicians accustomed to the piano and similar keyboard instruments to acquire skill with the presently described instrument. In another particular implementation, shown in  FIG. 5 , the keys are arranged along a curved surface, allowing more compact embodiments of the instrument and lending a unique feel and appearance. 
     Some implementations may feature a cable linkage system, an example of which is shown schematically in  FIG. 6 , to connect the actuators  100  to vibratable strings  30 . In  FIG. 6 , actuators  100  are keys as described above. Cables  110  are wound around knurled shafts  140  that are mounted on the keys. Depressing the keys causes the keys to act as levers around one or more fulcrums  150 , pulling cables  110 . Cables  110  are wrapped around a distribution ring  160 , which may be a cylinder, and fan out toward vibratable strings  30  such that they displace vibratable strings  30  toward movable member  20  when pulled. Distribution ring  160  need not be orthogonal to the plane formed by the lengths of cable  110  extending between actuator  100 , distribution ring  160 , and vibratable string  30 . This allows an arrangement of actuators  100  that does not share the same curvature as movable member  20 . 
     Referring to  FIG. 7A , in a particular implementation, bridge  60  is attached to soundboard  80  by bridge feet  90 . The bridge  60  rests on a pivot post  170 , which is directed upwards through the soundboard  80  toward the bridge  60 , and is threaded such that it can be raised and lowered like a screw. The bridge preferably vibrates freely around an axis parallel to the axis of rotation of driving mechanism  10 . Raising the pivot post  170  forces the bridge  60  away from the soundboard  80 , decreasing the normal force applied to the bridge  60  by the soundboard  80  via the bridge feet  90 . Conversely, lowering the pivot post  170  increases said normal force. Manipulating said normal force adjusts the amplitude with which the soundboard  80 , connected to the bridge  60  via bridge feet  90 , will vibrate relative to the pivot post  170 . Increasing this amplitude will result in a higher perceived volume, as the soundboard  80  is able to effect larger changes in acoustic pressure.  FIGS. 7B ,  7 C, and  7 D illustrate bottom views of the adjustable pivot post  170 . 
     Soundboards  80  of various shapes may be employed.  FIG. 8  shows an implementation where the soundboard  80  is a planar surface. Because of its resonance characteristics, the planar soundboard  80  may result in superior acoustic qualities in comparison to soundboards of other shapes. 
       FIG. 9  shows an implementation where the soundboard  80  is a cylindrical surface. A soundboard  80  of this shape may result in the instrument being more compact and may lend it a distinct appearance. 
     The driving mechanism  10  can be motorized.  FIG. 10  shows an implementation in which the driving mechanism  10  is turned by a motor  180 , via a pulley system  190 .  FIG. 11  shows a motor speed controller unit  200  that allows the driving mechanism  10  to be rotated at various speeds, allowing the user to mechanically vary the volume of the instrument. 
     The driving mechanism  10  can also be human-powered.  FIG. 12  shows an implementation in which the driving mechanism  10  is turned by a treadle wheel  210 , which is itself turned by a pedal  220  that is depressed by the user&#39;s foot. 
     Some implementations feature a means for converting string vibration to an electrical signal. For example,  FIG. 13  illustrates three such means: an electromagnetic pickup  230  placed near a vibrating metal string  30  such that the changes in magnetic flux generate an electrical signal; a piezoelectric transducer  240 , attached to the bridge  60 , that converts the vibrations of the bridge  60  to an electrical signal; and a microphone  250  that converts changes in acoustic pressure into an electrical signal. 
     Actuators  100  may comprise a plurality of electromagnetic switches, such as solenoids or relays, that each bring a corresponding vibratable string  30  into contact with the movable member  20  when the switch is opened or closed via an electrical or magnetic signal.  FIG. 14  illustrates one such example system, in which each vibratable string  30  corresponds to one solenoid  260 . Electromagnetic switching systems allow operation without real-time human input. For example, the solenoids  260  in  FIG. 14  could be controlled by electrical signals conforming to the Musical Instrument Digital Interface (MIDI) standard. These signals may be prerecorded, allowing the instrument to play notes without real-time human assistance, similar to a player piano. Circuit board  310  is a digital interface that allows MIDI signals to control actuators such as solenoids. 
     Some implementations employ one or more vibratable strings  30 , known as “drone strings,” that remain in contact with the movable member  20  even without actuation. As one example, referring to  FIG. 6 , drone strings  30  can be employed simply by sufficiently lowering the height of the vibratable string  30  relative to the movable member  20  (the “action”). 
     Some implementations feature a means for attenuating the amplitude of the vibrations of vibratable strings, for example, a string dampening mechanism that attenuates the amplitude of a vibrating string  30  to generate muffled or staccato tones. In  FIG. 15 , an example of such a means is shown: a dampening apparatus, such as an array of metal strips with foam damping pads  270  underneath, is raised and lowered onto vibratable strings  30  via a foot pedal  280  to engage and disengage the dampening effect. 
     Some implementations feature a means for modulating the pitch or volume of a vibratable string while the string is vibrating, for example to simulate the finger-based volume and pitch adjustments possible with a violin. For example, the trill mechanism shown in  FIG. 16  engages a spring-loaded artificial “finger”  290  to press one of strings  30  against movable member  20 . (This mechanism may act in parallel with the cable linkage system described above, such that either the trill mechanism or a cable-linked actuator  100  may press one of vibratable strings  30  against movable member  20 .) The trill mechanism may thus be used to create staccato or tremolo effects, where a note is repeatedly played and released in a rhythmic pattern.  FIG. 16  also illustrates a vibrato mechanism that adjusts the tension of a vibratable string  30  to create small adjustments in the pitch of a played note. In the example shown, the mechanism consists of an artificial “finger”  300  placed in contact with one of vibratable strings  30  and moved along the length of the vibratable string  30  by means of a cable linkage system such as described above. Moving the finger as such changes the effective length of the vibratable string  30  and thus changes the pitch of the note played as the string vibrates.