Patent Publication Number: US-6703553-B2

Title: Chorded musical instrument

Description:
RELATED APPLICATIONS 
     The present application is based on U.S. Provisional Patent Application No. 60/238,788, filed Oct. 6, 2000, entitled ELECTRONIC INTERFACE FOR A STRINGED INSTRUMENT, and incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to stringed musical instruments, particularly to such instruments having an electronic interface. 
     BACKGROUND INFORMATION 
     Musical instruments having electronic signal interfaces are well known. One such interface is an analog signal interface, which provides a faithful analog signal representation of the sound generated by the instrument. Another commonly used interface of more recent origin is the Musical Instrument Digital Interface (MIDI). The MIDI interface provides for the exchange of digital signals in accordance with a standardized protocol. MIDI interfaces are common on musical instruments such as keyboards and six string guitars. 
     Other musical instruments, however, such as double stringed instruments, have not been provided with MIDI interfaces. 
     SUMMARY OF THE INVENTION 
     In accordance with an exemplary embodiment of the present invention, a stringed instrument is provided incorporating several novel aspects. 
     In a first aspect, the present invention provides a novel bridge which allows the arrangement thereon of piezoelectric pickups in closely spaced groups, such as pairs. 
     In a further aspect, the present invention provides a novel piezoelectric pickup which can be arranged collinearly with the chord with which it makes contact. This allows for a compact arrangement with closely spaced strings. 
     In yet a further aspect, the pickups can be coupled to a signal processing device in one of several arrangements that allow for the generation of MIDI and analog signal representations of the string vibrations. In accordance with the present invention, the number of strings and pickups can exceed the number of signal inputs of the signal processing device. 
     In a further embodiment, the present invention provides a double stringed instrument having octave tuning with a MIDI interface. The present invention can be applied to any double stringed instruments that have the same tuning in unison or in octave, such as the bouzouki, the mandolin, the twelve string guitar, the oud and the saz. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A through 1D show various views of an exemplary embodiment of a bridge in accordance with the present invention. 
     FIGS. 2A and 2B show a conventional piezoelectric pickup. FIGS. 2C and 2D show an exemplary embodiment of a piezoelectric pickup in accordance with the present invention. 
     FIGS. 3A through 3D show various components of a commercially available signal processing device for use in the present invention. 
     FIG. 4 shows an exemplary grouping of strings. 
     FIG. 5 shows an exemplary connection scheme of piezoelectric pickups to inputs of the signal processing device, in accordance with the present invention. 
     FIG. 6 shows a further exemplary connection scheme of piezoelectric pickups to inputs of the signal processing device, in accordance with the present invention. 
     FIGS. 7A and 7B show an exemplary embodiment of a musical instrument in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to several aspects of an improved stringed musical instrument, including a novel bridge for piezoelectric (or “piezo”) pickups (FIGS.  1 A- 1 D), a piezo pickup comprising a novel coupling configuration (FIGS. 2A-2D) and a novel interface between the piezo pickups and a signal processing device (FIGS.  5  and  6 ). 
     FIG. 1A shows a front view of an exemplary embodiment of 15 a bridge  100  in accordance with the present invention. FIG. 1B shows a top view of the bridge  100 . The bridge  100  comprises four slots for mounting four pairs of piezo pickups  200  thereon. The bridge  100  comprises a central portion  110  upon which the piezo pickups  200  are mounted. 
     Eight thru-holes are provided through the bridge  100  for passing therethrough wires for coupling to the eight piezo pickups  200 . 
     In an exemplary embodiment, the bridge  100  has a length of 160 mm, and a thickness of 8 mm at the ends and 10 mm at 4 the central portion  110 , where the piezo pickups are placed. Each of the four slots has a width of 6.15 mm. The central portion  110  of the bridge  100  has a length of 41.66 mm. The diameter of each of the 8 thru-holes is 1.25 mm. Naturally, the actual dimensions can be selected as required. 
     FIG. 1C shows the bridge  100  with the 8 piezo pickups  200  in place FIG. 1D shows a cross-sectional view of the bridge  100  with a piezo pickup in place. A cable coupled to the pickup is also shown. 
     A further aspect of the present invention relates to the piezoelectric pickups  200 . FIG. 2A shows a front view of a conventional piezo pickup in its original configuration, and FIG. 2B shows a side view of the same pickup. Each pickup  200  comprises a base  210  and an upper portion  220  which is adapted 15 to contact a string  400 . The upper portion  220  is coupled to the base  210  via junctions  215  arranged at opposite ends of the piezo pickup. The junctions  215  allow the upper portion  220  to move relative to the base  210 . 
     The vibrations of the string  400  are transferred by the 20 upper portion  220  to a piezoelectric crystal  230  arranged in the base  210 . The piezoelectric crystal  230  generates an electrical signal representative of the string&#39;s vibrations. 
     As seen from above, each piezo pickup  200  has a generally rectangular footprint. With the conventional pickup of FIGS. 2A and 2B, the length of the pickup is generally perpendicular to the string  400 . 
     In accordance with the present invention, each piezo pickup  200  is modified by providing a groove  225  along the top surface of the upper portion  220 . The groove  225  runs lengthwise, parallel with the length of the pickup  200 . The groove  225  receives therein a string  400 . This modification allows the pickup  200  to be oriented with its length along the string, thereby allowing the pickups to be placed closely next to each other to accommodate closely spaced strings. In the exemplary embodiment shown, the strings are arranged in pairs. FIG. 2C shows a front view of a piezo pickup  200  as modified in accordance with the present invention. FIG. 2D shows a side view of the modified piezo pickup  200  of the present invention. 
     In an exemplary embodiment, the groove  225  has a depth of 0.014 mm and a width 0.028 mm and is generally semicircular in cross-section. Naturally, the dimensions and cross-section of the groove  225  can be selected in accordance with the diameter  20  and cross-section of the string  400 . 
     The piezo pickups are coupled to a signal processing device  300 , such as the Poly-drive IV, available from RMC Industries. The Poly-drive IV comprises three circuit board assemblies (FIGS.  3 A- 3 D). In accordance with exemplary embodiments of the present invention, the piezo pickups can be coupled to inputs of the signal processing device in two different arrangements as depicted in FIGS. 5 and 6, respectively, so as to produce two distinct types of signals, MIDI signals, and analog signals representative of the actual acoustic sound generated by the instrument. MIDI generated sounds and the acoustic sound can be heard either simultaneously or separate from each other. 
     FIGS. 3A-3D show the Polydrive IV system which is composed of two assemblies. As shown in FIG. 3C, the first assembly has two boards, board  1  and board  2 , and includes all input connections (shown in FIG. 3A) for the piezo pickups as well as a 13-wire ribbon cable that connects board  2  to a third board, board  3 . The signal inputs of the signal processing device are labeled  1 - 6  and each includes a signal input pad and a ground pad. A signal conductor couples the signal output of each piezo pickup to a signal input pad and a ground conductor couples the ground of each piezo pickup to a ground pad. (See FIGS. 5 and 6, described more fully below.) The signal and ground conductors of each piezo pickup can be arranged in a shielded cable, as shown in the various illustrations. 
     As shown in FIGS. 3B and 3D, the second assembly includes board  3 , which comprises a standard 13-pin MIDI jack for coupling to a MIDI interface, and a standard 4 inch jack for coupling to an amplifier. 
     To more clearly illustrate the connections of the piezo pickups to the Poly-drive IV, the instrument&#39;s strings can be divided into two groups, A and B. Group A includes strings A 1 , A 2 , A 3  and A 4  and group B includes strings  91 , B 2 , B 3  and B 4 . As shown in FIG. 4, A 1 B 1 , A 2 B 2 , A 3 B 3  and A 4 B 4  are representations of the strings D (RE), A (LA), F (FA) and C (DO) respectively; i.e., A 1 B 1  represents the two strings of D  10  (RE), A 2 B 2  represents the two strings of A (LA), etc. 
     An exemplary connection scheme, referred to as type  1 , is illustrated in FIG.  5 . The pickups of the strings of groups A, strings A 1 , A 2 , A 3  and A 4 , are connected to inputs  1 ,  2 ,  3  and  4 , respectively, of the signal processing device  300 . The 15 pickups of the strings B 1  and B 2  are connected to input  5  of the signal processing device  300 , whereas the pickups of the strings B 3  and B 4  are connected to input  6 . In the embodiments shown inputs  5  and  6  of the signal processing device have been modified to inhibit the production of MIDI sound. 
     Also shown in FIG. 5 are slide switches on board  1  which control various functions such as Bass, Treble, Mid-Range, Volume and MIDI Volume. 
     A further exemplary connection scheme type  2 , is shown in FIG.  6 . The pickups of strings A 1  and B 1  are connected to input  1  of the signal processing device  300 , the pickups of strings A 2  and B 2  are connected to input  2 , the pickup of string A 3  is connected to input  3 , the pickup of string A 4  is connected to input  4 ; the pickup of string  93  is connected to input  5 ; and the pickup of string B 4  is connected to input  6 . For clarity, in FIGS. 5 and 6, the signal and ground conductors of each piezo pickup are shown as one cable. As described above, it is understood that the ground conductors are coupled to the ground pads of the inputs  1 - 6  and the signal conductors are coupled to the signal input pads of the inputs  1 - 6 . Furthermore, the connections shown in FIGS. 5 and 6 are for the RMC Industries Poly-drive IV. Different connection arrangements may be required for different signal processing devices. 
     Both connection types  1  and  2  allow the production of MIDI signals and analog signals either simultaneously or separate from each other. 
     FIG. 7A shows a top view of an exemplary embodiment of a musical instrument in accordance with the present invention. The instrument of FIG. 7A comprises a bouzouki modified in accordance with the present invention to include exemplary embodiments of the above-described inventive bridge, piezo pickups and signal processing interface. 
     FIG. 7B is a cross-sectional side view of the instrument of FIG.  7 A. 
     As can be understood to a person of ordinary skill in the art, the present invention is not limited to the exemplary embodiment illustrated.