Abstract:
An electric percussion unit and small-sized speakers are detachably connected to a trunk of an electric frame guitar, and a circuit board, on which electric circuit components required for generating tones and percussion sound are mounted, and a battery unit are housed in the trunk; while a guitarist is playing a flamenco on the electric frame guitar, the guitarist beats the percussion unit with his or her hand or finger nails, and the guitar tones and percussion sound are radiated from the small-sized speakers; the electric frame guitar system is available for a wide variety of music genres, and the portability is enhanced.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to an electric stringed musical instrument and, more particularly, to an electric stringed musical instrument of the type having a frame body and an electric stringed musical instrument system including an electric stringed musical instrument and a sound generating system.  
         DESCRIPTION OF THE RELATED ART  
         [0002]    Electric guitars belong to the electric stringed musical instrument. Players usually sling the electric guitars over their shoulders with straps, and pluck the strings so as to give rise to vibrations of the strings. The vibrations of the strings are converted to electric signals by means of pickup units, and the electric tones are radiated from the associated sound systems. Various sorts of electric guitars have been proposed and sold in the market. Electric guitars with solid bodies have been popular to the guitarists. The electric guitars have solid bodies, and necks project from the solid bodies. Strings are stretched over the necks, and the pickup units are provided under the strings. The solid body is made from a wood panel or of synthetic resin, and silver fir or spruce is preferable for the solid body. Although several sorts of solid bodies are formed with hollow spaces, the hollow spaces are not expected to serve as resonators, because the amplifiers increase the loudness of the electric tones.  
           [0003]    Nevertheless, some electric guitars have bodies formed with resonators, and are called as “electric acoustic guitar”. The non-solid body is fabricated from deck boards and a sideboard. The deck boards and sideboard define the resonator, and a center block of maple reinforces the non-slid body.  
           [0004]    The electric guitars are equipped with electromagnetic pickup units, and the electromagnetic pickup units convert the vibrations of steel strings to the electric signals. Pressure-sensitive pickup units may be employed in other electric guitars. In this instance, nylon strings or gut strings may extend over the pressure-sensitive pickup units.  
           [0005]    Thus, various sorts of bodies, pickup units and strings result in a wide variety of electric guitars. As described hereinbefore, the resonators are not required for the electric guitars with the exception of the electric acoustic guitars. Frame bodies have been proposed for the electric guitars. The frame bodies are so light that guitarists feel the electric guitars easy to keep them around the waists.  
           [0006]    [0006]FIG. 1 shows a typical example of the electric guitar  1 . The prior art electric guitar  1  comprises a frame body  2 , a trunk  3  and strings  4 . The trunk  3  serves as a boss  3   a  and a neck  3   b . The frame body  2  is separable into three frame pieces  2   a ,  2   b  and  2   c , and the frame piece  2  and pieces  2   b / 2   c  sideward project from the both side surfaces of the boss  3   a . A fingerboard  5  is adhered to the upper surface of the neck  3   b , and frets  6  are embedded in the fingerboard  5  at intervals. The strings  4  are made of nylon, and are stretched over the frets  6 . A peg box  7  are fixed to the boss  3   a , and pegs  8  are rotatably supported by the peg box  7 . The strings  4  are wound on the pegs  8 , and bridges  9  and  10  make the strings  6  floating over the frets  6 . A pickup unit is provided between the upper surface of the trunk  3   a  and the bridge  10 , and converts the vibrations to an electric signal. The electric signal is electrically amplified, and is converted through a speaker system to sound. Thus, the vibrations of strings are magnified without any mechanical resonator.  
           [0007]    The frame pieces  2   a ,  2   b  and  2   c  make users to image the outline of the conventional guitar body. The frame pieces  2   b  and  2   c  are connected to the left side of the trunk  3 , and the other frame piece  2   a  is connected to the right side of the trunk  3 . The frame bodies  2   a / 2   b / 2   c  are detachable from the trunk  3   a . The detachable frame body  3  is desirable for users, because they package the trunk  3  and frame body in a small case. The electric guitars with frame bodies are hereinbelow referred to as “electric frame guitars”.  
           [0008]    The frame body  2  is so light and easy for packaging that the manufacturers supply various models of frame guitars to the music market. Many pop musicians and rockers give their performances on the frame guitars to the music fans. However, the prior art frame guitars are not available for some music genres. For example, while a guitarist is performing a piece of flamenco music, the guitarist not only plucks the strings but also beats the body. Spanish guitars are used in the performance, and have resonators in the bodies. When the guitarist beats the body, the resonator enlarges the beats, and the melody and rhythm make the flamenco music impressive. Thus, the beats are unique feature of the flamenco. This means that the prior art electric frame guitars are useless, because there is not any board to be beaten. Moreover, even if a board is attached to the frame body  2 , the beats are not enlarged, and the guitar sound drowns out the beats.  
           [0009]    Another problem inherent in the prior art electric frame guitar is portability of the electric guitar system. When a guitarist practices the prior art electric frame guitar, the guitarist is to connect the pickup unit through a cable to amplifiers, to which a speaker system is to be connected through a cable. When he or she moves to another studio, he or she disconnects the prior art electric frame guitar from the amplifiers and the amplifiers from the speaker system, and conveys the amplifiers and speaker systems to the studio together with the prior art electric frame guitar.  
         SUMMARY OF THE INVENTION  
         [0010]    It is therefore an important object of the present invention to provide an electric stringed musical instrument available for the music genres requiring beats as well as tones.  
           [0011]    It is also an important object of the present invention to provide an electric stringed musical instrument system, which is compact and portable.  
           [0012]    In accordance with one aspect of the present invention, there is provided an electric stringed frame musical instrument for generating electric tones comprising a trunk having a surface, at least one string connected at both end portions thereof to the trunk and stretched over the surface, a frame body connected to the trunk, a pickup unit provided under the aforesaid at least one string and converting vibrations of the aforesaid at least one string to a first electric signal representative of electric tones to be generated, and an electric percussion unit connected to the trunk and beaten for generating a second electric signal representative of percussion sound to be generated. In accordance with another aspect of the present invention, there is provided an electric stringed frame musical instrument for generating electric tones comprising a trunk having a surface, at least one string connected at both end portions thereof to the trunk and stretched over the surface, a frame body detachably connected to the trunk, a pickup unit provided under the aforesaid at least one string and converting vibrations of the aforesaid at least one string to an electric signal representative of electric tones to be generated, and a signal processing system provided inside of the trunk, connected to the pickup unit for receiving the electric signal and including a speaker detachably connected to the trunk for radiating the electric tones on the basis of the electric signal. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The features and advantages of the electric stringed musical instrument and the electric stringed musical instrument system will be more clearly understood from the following description taken in conjunction with the accompanying drawings, in which  
         [0014]    [0014]FIG. 1 is a plan view showing the structure of the prior art electric frame guitar,  
         [0015]    [0015]FIG. 2 is a perspective view showing an electric frame guitar and a sound generating system of an electric guitar system disassembled from one another,  
         [0016]    [0016]FIG. 3 is a plan view showing the electric guitar system in assembled state,  
         [0017]    [0017]FIG. 4 is a cross sectional view showing frame pieces connected to a trunk,  
         [0018]    [0018]FIG. 5 is a cross sectional view showing a percussion unit incorporated in the electric frame guitar, and  
         [0019]    [0019]FIG. 6 is a block diagram showing the system configuration of the sound generating system. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    Referring to FIG. 2, an electric guitar system embodying the present invention largely comprises an electric frame guitar  21  and a sound generating system  22 . A guitarist plucks the electric frame guitar  21  and beats it in his or her performance, and the electric frame guitar  21  generates an electric signal representative of tones to be generated and another electric signal representative of beats to be also generated. The electric signals are supplied from the electric frame guitar  21  to the sound generating system  22 , and the sound generating system  22  converts the electric signals to the tones and beats. The electric frame guitar  21  is firstly described hereinafter.  
         [0021]    The electric frame guitar  21  includes a trunk  23 , a frame body  24 , six strings  25   a ,  25   b ,  25   c ,  25   d ,  25   e  and  25   f , pegs  26 , bridges  27 / 28 , a tailpiece  29 , a pickup  30  and a strap  31 . The trunk  23  is made of wood, and is partially thick and partially thin. The thick portion is referred to as “boss”, and the boss is labeled with reference “ 23   a ”. On the other hand, the thin portion is referred to as “neck”, and the neck is labeled with reference “ 23   b”.    
         [0022]    The neck  23   b  has an upper surface substantially coplanar with the upper surface of the boss  23   a , and a leading end portion  23   c  of the neck  23   b  is downwardly bent from the remaining portion of the neck  23   b . Six holes  23   d  are formed in the leading end portion  23   c , and the pegs  26  are rotatably supported in the holes  23   d  by the leading end portion  23   c . A fingerboard  32  is adhered to the upper surface of the remaining portion of the neck  23   b , and the bridge  27  is embedded in the neck  23   b  at the boundary between the leading end portion  23   c  and the remaining portion. Frets  33  are embedded in the fingerboard  32  at intervals. The frets  33  extend in the lateral direction of the fingerboard  32 , and are spaced from one another in the longitudinal direction of the fingerboard  32 .  
         [0023]    A bridge  28  is embedded in the tailpiece  29 , and is exposed to the upper surface of the tailpiece  29 . The tailpiece  29  is fixed to the upper surface of the boss  23   a . The pickup unit  30  is further embedded in the tailpiece  29 , and vibrations of the bridge  28  are propagated to the pickup unit  30 . The pickup unit  30  may be same as the pickup unit disclosed in Japan Patent Application laid-open No. 2000-267668.  
         [0024]    A hollow space is formed in the boss  23   a , and a battery  34  and a circuit board  35  of the sound generating system  22  are received in the hollow space. The pre-amplifier AM is connected to the pickup  26 , and is powered with the battery BA. Dials, switches (not shown) and sockets are provided on the outer surface of the boss  23   a , and are manipulated by users.  
         [0025]    The strings  25   a  to  25   f  are anchored to the tailpiece  29 , and extend over the upper surface of the boss  23   a  and the fingerboard  32 . The strings  25   a  to  25   f  are connected at the other ends thereof to the pegs  26  so that a user exerts tension on and removes the tension from the strings  25   a  to  25   f  by turning the pegs  26 . When the user exerts the tension on the strings  25   a  to  25   f , the strings  25   a  to  25   f  are pressed to the bridges  27  and  28  at both end portions thereof. However, the strings  25   a  to  25   f  float over the frets  33  between the bridges  27  and  28 . The strings  25   a  to  25   f  are different in thickness, and different registers are respectively assigned to the six strings  25   a  to  25   f . The string  25   a  is the thickest of all, and the lowest register is assigned thereto. The string  25   f  is the thinnest, and the highest register is assigned thereto.  
         [0026]    The frame body  24  is made of metal, alloy, synthetic resin or wood, and has a contour like the outline of the rigid body of the prior art electric guitar. In this instance, the frame body  24  is separated into two frame pieces  24   a  and  24   b . Although the frame piece  24   b  is fixed to the boss  23   a , the frame piece  24   a  is detachably connected to the boss  23   a.    
         [0027]    The frame piece  24   a  is constricted at the intermediate portion, and plugs  24   c / 24   d  project from both ends of the frame piece  24   a . The frame piece  24   a  is connected at both ends thereof to the trunk  23 , and the remaining portion is spaced therefrom. A hollow space  36  takes place between the side surface of the trunk  23  and the frame piece  24   a.    
         [0028]    On the other hand, the frame piece  24   b  is gently curved, and a grip  24   e  projects from the frame piece  24   b . The frame piece  22   b  is fixed to the side surface of the boss  23   a , and is not detachable. The frame piece  24   b  is also connected to both ends thereof to the trunk  23 , and the remaining portion is spaced therefrom. Another hollow space  37  takes place between the side surface of the trunk  23  and the frame piece  24   b.    
         [0029]    The strap  31  is popular to guitarists, and various sorts of straps are sold in the market. The strap  31  is one of the standard straps. The strap  31  has a flexible belt  31   a  and a pad  31   b . Holes  31   c / 31   d  are formed at both end portions of the flexible belt  31   a . The pad  31   b  is slidable on the flexible belt  31   a  so that the user can adjust the pad  31   b  to his or her shoulder.  
         [0030]    The frame piece  24   a  is detachably connected to the side portion of the trunk  23  with the plugs  24   c / 24   d , and the other frame piece  24   b  is fixed to the other side portion of the trunk  23 . The strap  31  is further connected to the rear/reverse surface portions of the trunk  23 .  
         [0031]    [0031]FIG. 4 shows the rear end portion  23   f  of the boss  23   a , to which the frame pieces  24   a / 24   b  and flexible belt  31   a  are connected at the rear ends thereof Since the frame pieces  24   a / 24   b  and flexible belt  31   a  are similarly connected at the other ends to the trunk  23 , description is focused on the rear end portion  23   f  The side surfaces, which are respectively close to the strings  25   a  and  25   f , are designated by reference numerals  23   h  and  23   j , respectively, and the rear end surface is labeled with reference  23   k.    
         [0032]    The rear end portion  23   f  is partially narrowed so that steps  23   k  and  23   m  take place between the wide sub-portion and the narrow sub-portion. The side surfaces of the narrow sub-portion are generally rectangular. A recess  23   n  is formed in the narrow sub-portion, and is open to the outside on the side surface. A sleeve  39   a  is loosely received in the recess  23   n  so that gap G takes place between the sleeve  39   a  and the inner surface defining the recess  23   n . The sleeve  39   a  has an inner diameter larger than the outer diameter of the plug  24   d . This means that the user can easily insert the plug  24   d  into the sleeve  39   a . The sleeve  39   a  is made of elastically or resiliently deformable material. The sleeve  39   a  of the elastically or resiliently deformable material is to be recovered to the cylindrical shape equal to the gap G after the elastic or resilient deformation.  
         [0033]    A generally rectangular plate  39   b  is attached to the side surface of the narrow sub-portion, and is fixed to the narrow sub-portion by means of wood screws (not shown). The generally rectangular plate  39   b  is made of metal or synthetic resin, and has the thickness approximately equal to the depth of the step  23   m . For this reason, the outer surface of the plate  39   b  is coplanar with the side surface  23   h . A through-hole  39   c  is formed in the generally rectangular plate  39   b , and is aligned with the inner space of the sleeve  39   a . The through-hole  39   c  has the inner diameter smaller in value than the outer diameter of the sleeve  39   a  so that the generally rectangular plate  39   b  prevents the sleeve  39   a  from dropping out from the recess  23   n . However, the through-hole  39   c  is larger in diameter than the inner diameter of the sleeve  39   a . The through-hole  39   c  permits the user to insert the plug  24   d  into the inner space of the sleeve  39   a.    
         [0034]    The plug  24   d  and sleeve  39   a  are fastened to the rear end portion  23   f  by means of a fastener  40 , and the flexible belt  31   a  is also fastened to the rear end surface  23   k  by means of the fastener  40 . Thus, the fastener  40  is shared between the frame piece  24   a  and the flexible belt  31   a.    
         [0035]    The fastener  40  includes a nut  40   a , a bolt  40   b , a knob  40   c  and a washer  40   d . A hole  23   p  is further formed in the rear end portion  23   f , and is open at one end to the recess  23   n  and at the other end to the outside on the rear end surface  23   k . The nut  40   a  is inserted into the hole  23   p , and is fixed to the rear end portion  23   f . The nut  40   a  is equal in length to the hole  23   p  so that the both end surfaces are coplanar with the inner surface defining the recess  23   n  and the rear end surface  23   k , respectively. The knob  40   c  is formed with serration, which prevents fingers from slippage. The knob  40   c  is fixed to the bolt  40   b , and the bolt  40   b  is engaged with the nut  40   a . The user pinches the knob  40   c  with fingers, and drives the knob  40   c  for rotation. Then, the bolt  40   b  deeply projects through the nut  40   a  into the recess  23   n , and is brought into contact with the outer surface of the sleeve  39   a . As described hereinbefore, the sleeve  39   a  is elastically or resiliently deformable. When the bolt  40   b  is pressed to the sleeve  39   a , the sleeve  39   a  is deformed, and is pressed onto the plug  24   d . Thus, the bolt  40   b  is pressed through the sleeve  39   a  to the plug  24   d , and prohibits the plug  24   d  from being pulled out.  
         [0036]    The holes  31   c  and  31   d  are formed in both end portions of the flexible belt  31   a . A bolt (not shown) passes through the hole  25   c , and is engaged with a nut embedded in the reverse surface portion of the trunk  23 . The bolt presses a washer (not shown) to the flexible belt  31   a , and the washer in turn presses the flexible belt  31   a  to the reverse surface of the trunk  23 .  
         [0037]    Similarly, the bolt  40   b  passes through the hole  31   d , and the washer  40   d  is pressed to the flexible belt  31   a . The washer  40   d  presses the flexible belt  31   a  to the rear end surface  23   k . Thus, the bolt  40   b  not only presses the sleeve  39   a  to the plug  24   d  but also pinches the flexible belt  31   a  between the rear end surface  23   k  and the washer  40   d . This means that the fastener  40  is shared between the frame piece  24   a  and the flexible belt  31   a . Only one knob  40   c  is seen around the rear end portion  23   f  of the trunk  23 , and the shared fastener  40  makes the outer appearance of the electric frame guitar  21  simple.  
         [0038]    The other plug  24   c  is fastened to the reverse surface portion of the trunk  23  by another fastener  42  in a similar manner to the plug  24   d . The fastener  42  is used for the flexible belt  31   a  as well as the plug  24   c . The fastener  42  is similar in structure to the fastener  40 , and is shared between the plug  22   c  and the flexible belt  31   a.    
         [0039]    The frame piece  24   b  is fixed to the rear end portion  23   f  by wood screws  43   a . Generally rectangular plates  43   b  are fixed to both ends of the frame piece  24   b , and are also made of metal or synthetic resin. Bolt holes are formed in the generally rectangular plate  43   b  at the rear end of the frame piece  24   b , and the generally rectangular plate  43   b  is attached to the narrow sub-portion. The wood screws  43   a  are screwed through the holes into the rear end portion  23   f , and presses the generally rectangular plate  43   b  to the side surface of the narrow sub-portion. The generally rectangular plate  43   b  has the thickness equal to the depth of the step  23   m  so that the outer surface of the plate  43   b  is coplanar with the side surface  23   j . Though not shown in the drawings, the other end of the frame piece  24   b  is similarly fixed to the side surface  23   j  of the trunk  23 .  
         [0040]    The sound generating system  22  includes the battery  34  and circuit board  35 . The sound generating system  22  further comprises a switching panel  51 , a pair of speaker units  52   a / 52   b  and a percussion unit  53 . Although the switching panel  51  is fixed to the side surface of the boss portion  23   a , the pair of speaker units  52   a / 52   b  and percussion unit  53  are detachably connected to the side surfaces of the boss portion  23   a . The speaker unit  52   a  is attached to the side surface same as the manipulating panel  51 . However, the other speaker unit  52   b  and the percussion unit  53  are selected attached to the other side surface of the boss portion  53   a.    
         [0041]    Various switches  51   a  such as, for example, a power switch, a volume control switch and a balance control switch are provided on the switching panel  51 , and a guitarist manipulates these switches  51   a . Some switches  51   a  are used for changing timbre of beat sound.  
         [0042]    The hollow spaces  36 / 37  are wide enough to receive the speaker units  52   a / 52   b . The speaker units  52   a / 52   b  include respective cases  52   c , diaphragms (not shown) and sets of plugs  52   d . Each set of plugs  52   d  projects from a side surface of the case  52   c , and the diaphragm is exposed to the upper surface of the case  52   c . Associated sockets  54  are embedded in the side surface portions of the boss portion  23   a , and are connected to the circuit board  34 . A guitarist inserts the sets of plugs  52   d  into the associated sockets  54 . Then, the speaker units  52   a / 52   b  are electrically connected to the circuit board  35 .  
         [0043]    The percussion unit  52  includes a case  53   a , pads P 1 , P 2 , P 3  and P 4  and plugs  53   b . The case  53   a  is made of rigid material such as, for example, metal, alloy or fiber-reinforced synthetic resin, and withstands the hitting power at beats. Plural holes  53   c  are formed in the case  53   a , and are stepwise decreased in cross section from the upper surface to the lower surface. Each of the pads P 1  to P 4  has a decorative plate  53   d , a metal plate  53   e  and a vibration sensor  53   f . The decorative plate  53   d  and metal plate  53   e  have a disc shape. The metal plate  53   e  is of the order of 1 millimeter thick. The decorative plate  53   d  is tightly attached to the metal plate  53   e  so that the beats give rise to vibrations of the metal plate  53   e . The vibration sensor  53   f  is implemented by a piezoelectric transducer, and is attached to the reverse surface of the metal plate  53   e . The piezoelectric transducers  53   f  are electrically connected to the plugs  53   b.    
         [0044]    The decorative plate and metal plate  53   e  are snugly received in the hole  53   c , and is secured to the case  53   a . The vibration sensor  53   f  is so small that the case  53   a  is spaced from the vibration sensor  53   f  Thus, the vibration sensor  53   f  freely vibrates, and converts the vibrations to an electric signal. The percussion unit  53  is so narrow that the hollow space  3  can receive the percussion unit  53  instead of the speaker unit  52   b.    
         [0045]    Users selectively assign timbres of beats to the pads P 1  to P 4  through the switches  51   a . A user may assign the timbre of beats generated through the beating of a body of a Spanish guitar with his or her hand to one of the pads P 1  to P 4 , and the timbre of beats tapped on the body with finger nails to another of the pads P 1  to P 4 . Another user may assign a timbre of drum sound to two of the pads P 1  to P 4  and a timbre of cymbal sound to the remaining pads. Yet another user may assign a timbre of rim shots at the rim of a snare drum to one of the two pads P 1  to P 4  and a timbre of head shots at the heat of the snare drum to the other pad. Similarly, the user may assign a timbre of cup shots at the cup portion of a hi-hat cymbal to one of the remaining pads and a timbre of flat shots at the peripheral portion of the hi-hat cymbal. Thus, the users arbitrarily assign timbres of beats to the pads P 1  to P 4 . Turning to FIG. 6 of the drawings, the circuit board  35  is connected to the pickup unit  30 , speaker unit  52   a  and percussion unit  53 . A signal processing system  55  is integrated on the circuit board  35 . The electric signal S 11  representative of the vibrations of the bridge  28  and electric signal S 12  representative of the vibrations of the pads P 1  to P 4  are supplied from the pickup unit  30  and vibration sensors  53   f  to the signal processing system  55 . Another electric signal S 13  may be further supplied from the external signal source (not shown) to the signal processing system  55 . The signal processing system  55  produces a tone signal S 14  on the basis of the electric signals S 11 /S 12 /S 13 , and supplies the tone signal S 14  to the speaker unit  52   a  or units  52   a / 52   b . Otherwise, the tone signal S 14  from a signal output terminal  56  to an external system.  
         [0046]    The signal processing section  55  is broken down into four sections. The first section is assigned to the pickup unit  30 , and includes an equalizer  55   a , a reverb generator  55   b , a mixer  55   c , a power amplifier  55   d  and a signal output circuit  55   e . The electric signal S 11  is representative of the vibrations of the bridge  28 , and the frequency spectrum is equalized through the equalizer  55   a . The electric signal S 11  is supplied from the equalizer  55   a  to the reverb generator  55   b . The reverb generator  55   b  includes an analog-to-digital converter, a digital signal processor DPS and a digital-to-analog converter. The electric signal S 11  is converted to a series of digital codes, and the digital signal processor processes the digital codes for imparting digital codes representative of the reverberation to the series of digital codes. The digital codes are converted to an electric signal S 15 , again, and the electric signal S 15  is supplied through the mixer  55   c  to the power amplifier  55   d . In case where the electric signal S 12  and/or S 13  is supplied to the signal processing system  55 , the electric signal S 15  is mixed therewith before transmitting it to the power amplifier  55   d . The power amplifier  55   d  produces the tone signal S 14 , and supplies it to the speaker unit or units  52   a / 52   b . Other wise, the mixer  55   c  supplies the signal through the signal output circuit  55   e  to the signal output terminal  56 .  
         [0047]    The second section is assigned to the pads P 1  to P 4 , and includes a signal input circuit  55   f , a tone controlling circuit  55   h  and a tone generator  55   j . While a player is selectively beating the pads P 1  to P 4 , the vibration sensors  53   f  supply the electric signal S 12  through the signal input circuit  55   f  to the tone controlling circuit  55   h . The signal input circuit  55   f  detects the electric signal S 12 , and shapes the waveform of the electric signal S 12 . The tone controlling circuit  55   h  is responsive to the electric signal supplied from the signal input circuit  55   f  so as to instruct the tone generator  55   j  the timbre or timbres of beat sound, pitches of the beat sound and duration to be maintained. The tone generator  55   j  fetches pieces of waveform information stored in a memory, and generates a digital tone signal under the control of the tone controlling circuit  55   h . The digital tone signal is converted to an analog tone signal S 16 . The analog tone signal S 16  is supplied from the tone generator  55   j  through the mixer  55   c  to the power amplifier  55   d  or signal output circuit  55   e.    
         [0048]    The third section is assigned to a built-in sound source  55   k  such as, for example, a compact disc or a floppy disc, and includes a floppy disc driver/controller  55   m  and a tone generator  55   n . In case where a compact disc serves as the built-in sound source  55   k , the floppy disc driver/controller  55 , is replaced with a compact disc driver/controller. Plural sets of music data codes such as MIDI (Musical Instrument Digital Interface) codes are stored in the floppy disc  55   k , and the floppy disc driver/controller  55   m  reads out the music data codes. The music data codes are supplied to the tone generator  55   n , and a tone signal S 17  is produced on the basis of the music data codes. The tone signal S 17  is supplied from the tone generator  55   n  to the mixer  55   c.    
         [0049]    The fourth section is assigned to the external signal S 13 , and includes a signal input circuit  55   p . The external signal S 13  is, by way of example, supplied from a compact disc player and/or cassette recorder/player to the signal input circuit  55   p . The external analog signal S 13  is transferred from the signal input circuit  55   p  to the mixer  55   c.    
         [0050]    Thus, the electric signal S 15 /S 13  and tone signals S 16 /S 17  are selectively supplied to the mixer  55   c , and are mixed into the analog tone signal S 14 . The analog tone signal S 14  is supplied from the mixer  55   c  through the power amplifier  55   d  or signal output circuit  55   e  to the speaker unit or units  52   a / 52   b  or the external system. When a user generates electric tones from an external speaker system, an external power amplifier is connected to the socket  57 , and the electric signal is supplied through the socket  57  to the external power amplifier.  
         [0051]    The electric frame guitar system according to the present invention is selectively used in at least three modes of operation, which are hereinbelow referred to as “standard electric guitar mode”, “percussion-assist mode” and “portable mode”.  
         [0052]    Neither speaker units  52   a / 52   b  nor percussion unit  53  is connected to the electric frame guitar  21  in the standard electric guitar mode. The frame body  24  and strap  31  are fastened to the trunk  23 , and a guitarist slings the electric frame guitar  21  over his or her shoulder. The external power amplifier may be connected to the socket  57 . The guitarist selectively plucks the strings  25   a  to  25   f  for his or her performance. If the guitarist does not want to disturb the neighborhood, he or she disconnects the external power amplifier from the electric frame guitar  21 . On the other hand, when a guitarist wants to radiate the electric tones from the external speaker system, he or she connects the external power amplifier to the electric frame guitar  21 . While he or she is performing a piece of music on the strings  25   a  to  25   f , the electric signal S 11  to supplied from the equalizer  55   a  through the socket  57  to the external power amplifier, and the electric tones are radiated from the speaker system at volume.  
         [0053]    When a guitarist wants to perform a piece of music in a certain genre such as, for example, flamenco, classic music or folk music together with percussion sound, he or she connects the percussion unit  53  to the electric frame guitar  21 . If the guitarist wishes to generate the electric tones at large volume, he or she further connects the speaker unit  52   a  to the trunk  23  or the external power amplifier to the socket  57 . While the guitarist is performing the piece of music, he or she beats the pads P 1  to P 4 , and the percussion sound is generated from the speaker unit  52   a  or external speaker system together with the electric guitar sound.  
         [0054]    A guitarist is assumed to play a piece of music on the electric frame guitar  21  at an open-air concert. He or she connects the speaker units  52   a / 52   b  to the trunk  23 . While the guitarist is performing the piece of music on the electric frame guitar  21 , the vibrating strings  25   a  to  25   f  give rise to vibrations of the bridge  28 , and the vibrations are converted to the electric signal S 11  by means of the pickup unit  30 . The electric signal S 11  is equalized, and the signal component representative of the reverberation is given to the electric signal S 11 . The electric signal S 15  is increased in magnitude, and the electric tones are radiated from the speaker units  52 /a  52   b.    
         [0055]    As will be appreciated from the foregoing description, the percussion unit  53  is attached to the electric frame guitar so that the guitarist generates the percussion sound together with the electric guitar sound. Although the electric frame guitar  21  does not have any mechanical resonator, the guitarist can perform pieces of music as if he or she plays them on a Spanish guitar or classic guitar. In the embodiment described hereinbefore in detail, the percussion unit  53  is detachable. The frame body  24  is further separable from the trunk  23 . Thus, the detachable percussion unit  53  and separable frame body  24  enhance the portability of the electric frame guitar system.  
         [0056]    Moreover, the speaker units  25   a / 25   b  are connected to the electric frame guitar  21  so that the users perform the pieces of music without any bulky sound/speaker system. In the above-described embodiment, the speaker units  52   a / 52   b  are detachable. The frame body  24  is further separable from the trunk  23 . Thus, the detachable speaker units  52   a / 52   b  and separable frame body  24  enhance the portability of the electric frame guitar system.  
         [0057]    The plugs  52   d  of the speaker unit  52   b  are same as the plugs  53   b  of the percussion unit  53 . This results in that the sockets  54  are shareable between the percussion unit  53  and the speaker unit  52   b . This means that the percussion unit  52   a  and the percussion unit  53  are concurrently available for the performance. The interface between the electric frame guitar  21  and the percussion unit/speaker unit  53 / 52   b  offers a wide variety of usage to the users.  
         [0058]    Although particular embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention.  
         [0059]    The present invention is applicable to another electric stringed musical instrument and electric stringed musical instrument system such as, for example, electric base.  
         [0060]    For example, the frame piece  24   b  may be also connected to the trunk  23  by means of a coupling mechanism shown in FIG. 4.  
         [0061]    The pads P 1  to P 4  may be increased or decreased. Only one pad or more than four pads are incorporated in the percussion unit.  
         [0062]    A circuit board  35  may be deleted from an electric frame guitar according to the present invention. In this instance, the electric signals S 11 /S 12  are supplied from the pickup unit  30  and vibration sensors  53   f  through suitable terminals to an external signal processing system corresponding to the electric signal processing system  55 .  
         [0063]    Only the first and second sections  55   a / 55   b / 55   c / 55   d / 55   f / 55   h  and  55   j  may be incorporated in the signal processing system  55 . This means that the third and fourth sections are deleted from the signal processing system  55 .  
         [0064]    The signal terminal  57  may be connected between the reverb generator  55   b  and the mixer  55   c.    
         [0065]    Any sort of pickup unit is available for the electric frame guitar. Piezoelectric transducer or transducers may be incorporated in the pickup unit. In case where steel strings are used, an electromagnetic pickup unit will be used for producing the electric signal S 11 . Optical sensors are also available for the electric frame guitar.