U.S. patent number RE31,019 [Application Number 06/162,777] was granted by the patent office on 1982-08-31 for stringless electronic musical instrument.
Invention is credited to Fred J. Evangelista.
United States Patent |
RE31,019 |
Evangelista |
August 31, 1982 |
Stringless electronic musical instrument
Abstract
Disclosed is an electronic musical instrument resembling a
guitar that is played like a guitar and sounds like a guitar;
however, it is stringless and has a plurality of flexible actuator
blade type members which are mounted on edge and are adapted to be
strummed or picked. Flexing of each actuator blade in either
direction closes one or more leaf type switches which controls the
amplified output of an electronic oscillator whose fundamental
operating frequency is further varied in accordance with finger
actuation of a plurality of fret-board switches. Although the
invention in its preferred embodiment is directed to a guitar-like
instrument, it is also applicable to other types and classes of
musical string instruments such as a violin.
Inventors: |
Evangelista; Fred J. (Severna
Park, MD) |
Family
ID: |
26859046 |
Appl.
No.: |
06/162,777 |
Filed: |
June 25, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
973801 |
Dec 28, 1978 |
04177705 |
Dec 11, 1979 |
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Current U.S.
Class: |
84/702; 84/711;
84/738; 84/741; 84/DIG.30; 84/DIG.7; 84/DIG.8; 984/346 |
Current CPC
Class: |
G10H
1/342 (20130101) |
Current International
Class: |
G10H
1/34 (20060101); G10H 001/00 (); G10H 001/02 () |
Field of
Search: |
;84/1.01,1.16,DIG.7,DIG.8,DIG.30 ;330/284,302 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1262745 |
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Mar 1968 |
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DE |
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1282428 |
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Nov 1968 |
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DE |
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Other References
Millman and Taub, "Pulse Digital Switching Waveforms," McGraw-Hill,
1965, pp. 50-54. .
Ward, Electronic Music Circuit Guidebook, 1975, pp. 43 and
156..
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Primary Examiner: Truhe; J. V.
Assistant Examiner: Isen; Forester W.
Attorney, Agent or Firm: Schwartz, Jeffery, Schwaab, Mack,
Blumenthal & Koch
Claims
I claim:
1. In an electronic musical instrument for simulating a stringed
instrument having a .[.body portion adapted to carry.]. tone
generating means .[.and a neck portion adapted to carry a
finger-board assembly coupled to said tone generator means.]. and
being operable to vary the tonal output thereof, the improvement
comprising:
tone generator means including an electrical oscillator circuit
.[.for each fundamental frequency desired to be simulated and.].
including switch operated circuit means .[.operable from said
fingerboard assembly.]. for selectively changing .[.the.]. tonal
.[.output.]. frequency .[.of said oscillator circuit.].;
.[.a respective.]. .Iadd.an .Iaddend.output amplifier circuit
coupled to said oscillator circuit and being energized in
accordance with the operative state of a player actuated switch
device; and
said player actuated switch device .[.consisting of.].
.Iadd.comprising .Iaddend.a relatively thin .[.flexible
blade-type.]. switch actuator member .[.mounted on edge in a
substantially upright position on the outer surface of said body
portion adjacent said fingerboard assembly,.]. .Iadd.having a pair
of sides and .Iaddend.being adapted .[.thereby.]. to be deflected
bi-directionally .[.transverse.]. .Iadd.transversely .Iaddend..[.to
said upright position.]. when strummed, struck, picked or plucked
or bowed by a player, and at least one pair of electrical switch
contacts located on each side of said actuator .[.element.].
.Iadd.member.Iaddend., wherein deflection of said actuator
.[.element.]. .Iadd.member .Iaddend.in either direction operates
one of said pair of switch contacts to energize said output
amplifier circuit.
2. The musical instrument as defined by claim 1 wherein said tone
generator means comprises a plurality of electrical oscillator
circuits and respective output amplifier circuits for a plurality
of fundamental frequencies and wherein the respective .[.flexible
blade-type.]. switch actuator members therefor are mounted side by
side .[.such that their respective upper edges are.]. substantially
parallel and oriented generally in line with the longitudinal axis
of the instrument.
3. The musical instrument as defined by claim 2 wherein said
.Iadd.switch actuator members are .Iaddend.blade-type switch
actuator elements .[.are.]. generally rectangular in shape with
their lengthwise dimensions oriented substantially parallel to the
longitudinal axis of the instrument.
4. The musical instrument as defined by claim 3 wherein the
lengthwise dimension of said actuator members spans a region of
.[.said body portion.]. .Iadd.the instrument .Iaddend.wherein a
stringed instrument is normally played.
5. The musical instrument as defined by claim 4 .[.wherein the.].
.Iadd.including .Iaddend.outer edges .[.of.]. .Iadd.on
.Iaddend.said generally rectangular switch actuator members
.[.are.]..Iadd., said outer edges being .Iaddend.substantially
co-planar to simulate the multiple strings of a lute type
instrument.
6. The musical instrument as defined by claim 4 .[.wherein the.].
.Iadd.including .Iaddend.outer edges .[.of.]. .Iadd.on
.Iaddend.said generally rectangular switch actuator members
.[.lie.]..Iadd., said outer edges lying .Iaddend.in selective
different planes to simulate the strings of a viol type
instrument.
7. The musical instrument as defined by claim 4 wherein said
generally rectangular actuator members have substantially the same
length and width dimensions.
8. The musical instrument as defined by claim .[.7.]. .Iadd.4
.Iaddend.wherein the length dimension is greater than the width
dimension.
9. The musical instrument as defined by claim 1 wherein said output
amplifier is energized by the application of a supply potential to
generate an audio output signal and wherein said at least one pair
of switch contacts is connected intermediate said supply potential
and said output amplifier circuit.
10. The musical instrument as defined by claim 9 wherein said
output amplifier circuit additionally includes .[.a compensated
balanced bridge.]. .Iadd.an .Iaddend.attenuator network coupled
intermediate said switch contacts and said amplifier circuit for
coupling said supply potential thereto.
11. The musical instrument as defined by claim 10 wherein said
output amplifier circuit comprises a transistor amplifier circuit
having a base input circuit and additionally including variable
base bias voltage means coupled to said base input circuit for
providing harmonic control of said audio output signal.
12. The amplifier circuit as defined by claim 11 wherein said
.[.compensated.]. attenuator network comprises at least two
resistive impedances and at least two capacitors coupled together
in a bridge circuit arrangement to the collector circuit of said
transistor amplifier, and
wherein said switch device includes plural electrical switch
contacts located on each side of said switch actuator element and
being operable consecutively by deflection of said actuator element
to apply said supply potential to selective circuit points of said
.[.compensated.]. attenuator network.
13. The musical instrument as defined by claim 11 wherein said
transistor amplifier comprises a class C type transistor
amplifier.
14. The musical instrument as defined by claim 9 wherein said
electrical oscillator circuit comprises a programmable unijunction
transistor oscillator having an RC time control circuit which is
adapted to be controlled by means of a set of fret-board switches
.[.located on said fingerboard assembly.].. .Iadd. 15. The musical
instrument as defined in claim 1 wherein said instrument includes a
body portion and a neck portion adapted to carry a fingerboard
assembly connected to said body portion, said fingerboard assembly
being coupled to said tone generator. .Iaddend..Iadd. 16. The
musical instrument as defined in claim 3 wherein said switch
actuator member is mounted in a vertical direction. .Iaddend.
.Iadd. 17. The musical instrument of claim 2 wherein said switch
actuator members are flexible. .Iaddend..Iadd. 18. An electronic
musical instrument for simulating a stringed instrument
comprising:
(a) tone generating means,
(b) an output amplifying means connected to said tone generating
means,
(c) player actuated switch means operatively connected to said
amplifying means,
(d) an attenuator network coupled intermediate said switch means
and said amplifying means,
(e) means including said amplifying means, said network and said
switch means for:
(1) producing an attack portion of an audio frequency envelope upon
initial actuation of said switch means from a normal state,
(2) sustaining a sound produced by said tone generating means for
as long as said switch is actuated, and
(3) dampening the sound gradually as said switch is allowed to
return to a normal state;
(f) said amplifying means comprising a transistorized amplifier
circuit, said network comprising at least two resistive impedances
and at least two capacitors coupled together in a bridge circuit
arrangement to a collector circuit of said transistor amplifier.
.Iaddend..Iadd. 19. An instrument as defined in claim 18 wherein
said switch means includes an actuator, a plurality of electrical
contacts being operable consecutively by movement of said actuator
to apply a supply potential to selective circuit points of said
network. .Iaddend..Iadd. 20. The musical instrument of claim 10, 12
or 18 wherein said attenuator comprises a compensated balanced
bridge attenuator.
Description
Background of the Invention
This invention relates to improvements in musical instruments and
more particularly to an electronic musical instrument for
simulating a stringed instrument.
On a conventional guitar, whether it is an acoustical type or an
electrically amplified type, the sounds originate from vibrating
strings which are set in motion by a picking or strumming action. A
note is selected by playing an open string or by fingering a string
on a particular fret position on the neck of the instrument. This
action serves to change the vibrating length of the string thereby
producing the vibrating frequency of the desired tone. Chords are
played by picking, plucking or strumming more than one string,
either sequentially or with one stroke of the hand. Accordingly, a
conventional guitar is played by fingering the strings on the neck
of the instrument with one hand, while picking or strumming the
strings with the other hand.
While stringless guitar-like musical instruments have been
disclosed, for example in U.S. Pat. Nos. 3,340,343, 3,555,166, and
3,666,875, these instruments in addition to having a plurality of
finger actuated switches located in a fret-board type of
arrangement on the neck of the instrument, also includes means
located on the body of the instrument, requiring it to be played
much like a keyboard instrument, e.g. an accordian wherein manual
depressions of an element is required.
The present invention on the other hand is directed to a stringless
instrument, which can be played using similar techniques to those
described above for a conventional guitar. Furthermore, a player
who has learned to play a conventional guitar can play an
instrument according to the subject invention immediately without
having to relearn new fingering positions for either the neck of
the instrument or for the body of the instrument, meaning that
melodies and chords and combinations thereof can be picked or
strummed with a conventional plectrum as well as plucked or
strummed with the hand in the conventional manner.
Summary
Briefly, the subject invention is directed to an electrically
controlled musical instrument embodying self-contained electronic
tone generation modulation and amplification circuitry for the
production of musical sounds by means of a plurality of relatively
thin flexible blade type switch actuator members which are mounted
on edge and are located on the front surface of the body of the
instrument in line with a fret-board switch assembly. The outward
edge of each actuator resembles the cross section of a string and
is adapted to be plucked, strummed, struck or bowed. Each flexible
blade type actuator is adapted to be flexed in either direction,
causing closure of one or more leaf type electrical switches which
are adapted to control the amplified output of an electronic
oscillator circuit whose fundamental operating frequency is adapted
to be further varied in accordance with the operation of finger
actuated fret switches located on the neck of the instrument.
The preferred embodiment of this invention will be disclosed
primarily in terms of a guitar-like musical instrument which
comprises one of the "lute" classes of strummable string
instruments. It will also become apparent that other instruments in
the lute class can be simulated in the same manner. Furthermore,
the inventive concept can be used for electronic simulation of
"viol" class of musical stringed instruments such as the violin,
cello and other instruments which are played with a bow as well as
those plucked with the hand.
It can be seen, therefore, that the primary object of the present
invention is to provide a stringless musical instrument which can
be played as though it were, in fact, a stringed musical
instrument.
Other objects and advantages will become immediately apparent as
the following specification is considered in conjunction with the
accompanying drawings.
Brief Description of the Drawings
FIG. 1 is a top plan view of a guitar-like musical instrument
broadly illustrating the preferred embodiment of the subject
invention;
FIG. 2 is a fragmentary cross sectional view taken along the lines
2--2 of the neck portion of the instrument shown in FIG. 1 and
being illustrative of one fret-key switch assembly;
FIG. 3 is an end sectional view of the fret-key switch assembly
shown in FIG. 2 taken along the lines 3--3;
FIG. 4 is a partial side elevational view of the body portion of
the instrument shown in FIG. 1;
FIG. 5 is a top plan view of an assembly of plural flexible blade
type actuator members mounted on the body of the instrument for
simulating individual strings;
FIG. 6 is an exploded end view of one of the flexible blade
actuator members shown in FIG. 5 together with respective switch
contact assemblies on either side thereof;
FIGS. 7A and 7B are illustrative side and end planar views of the
type of flexible blade assembly utilized for lute type
instruments;
FIGS. 8A and 8B are side and end planar views of the type of
flexible blade assembly utilized for viol type instruments; and
FIG. 9 is an electrical schematic diagram illustrative of the
circuit details for one of six flexible actuator blade members and
its interconnection with the remaining five simulated strings to
form a complete electronic system for generating musical
sounds.
Description of the Preferred Embodiment
Referring now to the drawings and more particularly to FIG. 1,
there is disclosed a top plan view of a guitar-type instrument 10
consisting of a body portion 12 and a neck portion 14. Along the
neck portion 14 of the instrument 10 is fret switch assembly
including a plurality of keys 16 arranged in sets along the face of
the finger board 18. Such apparatus is well known to those skilled
in the art, a typical example being shown for example in the above
referenced U.S. Pat. Nos. 3,555,166 and 3,666,875.
On the upper face 20 of the body portion 12 is located an assembly
22 of six identical string simulation means which will be discussed
in detail to permit a player experienced with a conventional
stringed instrument to immediately play the subject instrument with
similar hand and finger motions applied to the assembly 22 in
addition to those established for the fret-switch keys 16 on the
finger board 18. Reference numeral 24 as shown in FIG. 6 generally
designates one of six identical flexible blade type switch actuator
members 24.sub.1, 24.sub.2 . . . 24.sub.6. This arrangement is
shown in detail in FIG. 5. The actuator members are generally
rectangular in shape as depicted in FIGS. 7A and 8A and are
relatively thin so as to permit flexure transversely to their
longitudinal dimension. As shown in FIG. 7A, the upper edge
26.sub.1 of member 24.sub.1 runs lengthwise for a predetermined
distance terminating in rounded corners 28. The members 24.sub.1 .
. . 24.sub.6 are of uniform thickness and when viewed from above as
shown in FIG. 5, are analogous to the cross section of a muscial
string located thereat in a conventional guitar-like
instrument.
Thus the flexible blade type elements 24.sub.1 -24.sub.6 can be
picked with a conventional type plectrum, plucked with fingers, or
strummed by both means with one stroke of the hand in either
direction in a normal manner. Accordingly, conventional finger,
hand and arm motions familiar to the musician experienced with
conventional stringed instruments are used. It should be noted that
the assembly 22 is preferably located at the conventional waist
region of the instrument body 12 on the longitudinal axis of the
instrument and that each flexible blade element 24.sub.1 . . .
24.sub.6 is parallely aligned with the neck portion 14 in the same
manner as the string it is intended to simulate. While mention of
the fact that the actuators 24.sub.1 . . . 24.sub.6 are generally
rectangular in shape, 1 is to be made that they are of sufficient
length along the longitudinal axis of the instrument to avoid the
need to search for their location when picking or strumming since
searching tends to detract from the normal motions already
cultivated by an experienced player of a conventional instrument,
particularly so in view of the fact that the body portion 12 is
observed to a much lesser extent than the neck portion 14.
A plurality of knobs 30, 32 and 34 are conveniently arranged on the
face 20 of the body portion 12 for effecting tone control, harmonic
control and a combination of the volume control as well as an
on/off switch, respectively. Reference numeral 36 is intended to
designate a suitable indicator light to indicate the power status
of the instrument. Also, shown in FIG. 1 on the surface 20 of the
body portion 12 is reference numeral 38 which is intended to
designate a muting switch pad associated with electronic circuitry,
not shown, which is used to provide abrupt sound cut off similar to
that accomplished when usable string vibrations are stopped with
the hand. For lute type instruments, it is preferred that the
muting switch pad 38 be located to serve as a rest for the heel of
the picking hand so that it can be depressed for muting instantly
without having to hunt for the pad.
Referring now to FIG. 2, there is disclosed the details of one
typical fret-switch key 16 shown in FIG. 1. A switch actuator
member 40 is held in its unactuated position against the underside
of the fingerboard 18 by means of resilient foam material
components 42 which are located at either ends of the element 40.
The durometer softness of the material from which the foam material
is comprised is selected to provide a comfortable feel to the
player, with considerations including low finger pressure but not
so low that undesired actuation can take place. A further
consideration is to provide a pre-travel of the member 40 downward
before a pair of electrical switch contacts 44 and 46 are closed.
The spring leaf configuration of member 44 permits over-travel
after the switch contacts close. The pre-travel aids to prevent
unwanted sounds from emanating when the element 40 is inadvertently
depressed by the fingers while using them for guidance or while
straddling them in a manner which is normal for playing stringed
instruments. The over-travel is provided for improved electrical
contact and to minimize finger fatigue, which may occur sooner when
stopped by an unyielding switch key.
Further to this end, it is preferred that the key element 40 be
permitted to be depressed so that the upper surface 48 is nearly
flush with the fingerboard surface 50, permtting only enough
protrusion to feel it for guidance when it is fully depressed.
Accordingly, when one of the key elements 40 is depressed, it is
guided to the proper location over the contact member 44 by means
of angulated guides which form an integral part of the contact
mounts 52 as shown in FIG. 3. These guides permit a freedom of fit
for the key element 40 in its finger-board slot so as to provide a
bind-free action.
An insulating board member 54 is used for mounting the contact
mount 52 with spacer bars 56 between each fret position. A multiple
pin connector, not shown, is utilized at the end of the mounting
board member 54 where it meets the body portion 12 to interface the
fret-key switch elements 16 with electronic circuitry shown in
schematic form in FIG. 9 contained inside of the body portion 12 of
the instrument.
The major improvement of the subject invention consists in the
actuator assembly 22 briefly referred to above and its related
electronic circuitry. Associated with each actuator element
24.sub.1, 24.sub.2 . . . 24.sub.6 is an assembly of six leaf type
switches arranged so that three switches are located on each side
of an actuator. Referring now to FIG. 6 which is intended to
typically illustrate one element 24 of the six identical structures
24.sub.1 . . . 24.sub.6, flexible leaf type electrical contact
strips 58.sub.a, 58.sub.b, 58.sub.c and 58.sub.d are located on one
side of the actuator 24 to form one set of switch contacts 58.
Mutual separation of the contact strips is provided by means of
electrical insulator members 60.sub.a, 60.sub.b, 60.sub.c and
60.sub.d. In a like manner, on the opposite side of the element 24
are electrical leaf type contact strips 62.sub.a, 62.sub.b,
62.sub.c and 62.sub.d and being separated from each other by means
of the insulator elements 64.sub.a, 64.sub.b , 64.sub.c and
64.sub.d. These form the other set of switch contacts 62. The
insulator elements 60.sub.a . . . 60.sub.d and 64.sub.a . . .
64.sub.d are preferably comprised of, for example, thin plastic
strips.
Additional insulation is provided by insulating sleeves 66 and 68
on a pair of contact mounting screws 70 and 72 with which nuts 74
and 76 respectively engage to hold the whole assembly together as
shown, for example, in FIG. 7B. The lower terminal portions of the
switch contacts 58.sub.a . . . 58.sub.d and 62.sub.a . . . 62.sub.d
comprise tab portions 78.sub.a, 78.sub.b, 78.sub.c and 78.sub.d and
80.sub.a, 80.sub.b, 80.sub.c and 80.sub.d for making electrical
connections to the electrical circuit elements shown in schematic
form in FIG. 9.
The flexible actuator type switch assembly shown in FIG. 6 can be
mounted singly or in multiples, depending on the type of instrument
desired. The arrangement shown in FIGS. 7A and 7B discloses a six
member configuration for simulating a lute-type instrument while
the configuration shown in FIGS. 8A and 8B comprise a four member
configuration simulating a viol-type instrument. In either case the
switch assemblies are ganged and spaced apart from one another
utilizing an end frame 82, a plurality of spacers 84 and mounting
screws and nuts 86 and 88.
Accordingly then, each of the actuators 24.sub.1 . . . 24.sub.6 are
comprised on thin flexible spring-like material which are mounted
on edge and project above the electrical contact strips and are
free to bend or deflect when a force normal to the upper playing
surface is applied. Since the contacts are mounted to the lower
portion of the actuators which is firmly held, it is possible to
bend the upper portion of the actuator by applying a small force
until, for example, electrical pole piece 58.sub.a as shown in FIG.
6 contacts element 58.sub.b, affecting a closing of one pair of
switch contacts. Initial movement in the other direction causes
elements 62.sub.a and 62.sub.b to make contact. Additional
incremental forces will cause additional sequential contact
closures to take place, namely element 58.sub.c would contact
element 58.sub.b and 58.sub.d would make contact with element
58.sub.c and so forth. When the force is removed, the actuator 24
and any contacts closed will return to their original upright
normally open condition as shown in FIG. 6. These events will take
place when the deflecting force is applied in either direction
normal to the plane face and nearer the top edge of the actuator
24. By this means the same magnitude of force applied in either
direction will close the same number of switch contacts and removal
of the force will allow the contacts to spring back to their open
state.
From the foregoing description it can be seen that if a guitar
player for example uses a conventional type plectrum to deflect the
actuator 24 shown in FIG. 6, first in one direction and then the
other, the picking action of a conventional guitar is simulated.
The actuators 24.sub.1 . . . 24.sub.6 as shown in FIG. 7B, for
example, may be deflected with a thumb or fingers or a combination
of both to provide a plucking action or when desirable, a complete
set of actuators 24.sub.1 . . . 24.sub.6 can be strummed with one
sweeping motion of the hand in either direction which is normal. It
should be emphasized here that all of the action described can be
performed by a musician already familiar with the guitar without
having to relearn new techniques or fingering positions.
With respect to the configuration for implementing the type of
string instruments in the "viol" class which includes those
instruments characteristically played with a fiddler's bow such as
a violin, cell, etc. reference to FIGS. 8A and 8B indicates that
the upper edges of four flexible actuators 24.sub.1 . . . 24.sub.4
are arranged in an arched profile similar to the bridge of a violin
making it possible to be played with a fiddler's type of bow, not
shown, to contact, when desired, only one simulated string at a
time. Such a configuration is possible because the electronic
circuitry shown in FIG. 9, to be discussed subsequently, in
addition to being utilized in connection with a guitar-type
instrument, is also designed such that: (1) the "attack" portion of
an audio frequency envelope is produced upon the initial deflection
of an actuator 24.sub.1 . . . 24.sub.4 rather than upon release as
is customary; (2) the sound is sustained for as long as the
deflection of the actuator is maintained by the dynamic friction of
the moving bow; and (3) the sound dampens gradually when the
actuator is allowed to return to its normal state upon lifting of
the fiddler's bow. Assuming that the actuator elements 24.sub.1 . .
. 24.sub.4 are made of thin flexible metallic material such that
the coefficient of friction at the thin top edge 26 is inadequate
for proper bowing, the edge may be capped with a plastic or similar
edging or beading elements 90.sub.1 . . . 90.sub.4 to provide a
proper friction factor. Alternatively, the actuator elements
24.sub.1 . . . 24.sub.4 etc. may be made from a plastic or similar
material which has been selected for optimum flexibility and
optimum friction factor. Accordingly, the subject invention is not
intended to be limited to the simulation of stringed instruments of
the lute class only, but rather it is intended to include the
simulation of other instruments in which the strings are played by
picking, plucking, strumming, bowing and also by known percussive
methods.
A major feature of the assembly 22 in its various embodiments as
shown in FIGS. 5 through 8B is the capability of producing
"expressive" variations in sound volume as a function of the amount
of actuator deflection of any element 24.sub.1 . . . 24.sub.n--1,
24.sub.n. It can be seen, for example, with reference to FIG. 6
that two sets 58 and 62 of three switches each are adapted to
provide three levels of expressive sound volume. The closest strip
58.sub.a and 62.sub.a on either side of the contact 24 is used as a
pole piece to provide a fixed supply potential V.sub.2 (FIG. 9) to
the remaining three contact strips 58.sub.b, 58.sub.c and 58.sub.d
and 62.sub.b, 62.sub.c and 62.sub.d, respectively. When the
actuator 24 deflects either strip 58.sub.a or 62.sub.a to its
nearest contact 58.sub.b or 62.sub.b the lowest level of sound will
be produced. As the deflection is increased, the second contact
58.sub.c or 62.sub.c is closed and a third 58.sub.d or 62.sub.d in
turn. As each contact closes against its neighbor, the expressive
sound volume increases to a higher level as will be shown. Although
three levels of expressive sound volume are illustrated, it should
be noted that if additional contacts are included in the stack,
then additional sound levels can be provided. This provision of
variations in sound volume enables the musician to perform with
"expression" using dynamic techniques similar to those applied to a
conventional string instrument, i.e. a greater string deflection
produces a greater volume of sound. Another important feature of
the subject invention is the capability of sustaining the sound
when desired by the musician during a musical score or as a part of
it without resorting to manipulation of other controls. This is
accomplished by holding or or more of the simulated strings, i.e.
actuators 24.sub.1 . . . 24.sub.n in the deflected position in
either direction. When they are released, the sound will dampen out
gradually. Also, "sustain" effects can be applied with increasing
or decreasing sound volume while the finger board keys 16 shown in
FIG. 1 are run through a musical sequence or while a particular
note or chord is held. The resulting advantage of this sustaining
feature is twofold, namely it provides an additional form of
"expression" for the musician when desired without detracting from
the normal method of playing the instrument, and the musician can
change the sound of the same instrument instantly to sound like a
plucked string instrument, an organ, or even a violin type
instrument.
In addition to the normal type of tone control provided by the knob
30 as shown in FIG. 1, a harmonic control is also provided by means
of the knob 32. With the control knob 32, the sounds are made to
vary in a manner which may be described as "timbre", "color",
"presence", etc. which when used in conjunction with the tone
control knob 30, can produce a wide range of tonal "voice"
variations. The uniqueness of this harmonic control function lies
in the simplicity of the circuit and its implementation which will
now be described.
Referring now to the schematic diagram shown in FIG. 9, the basic
audio frequency signals to be generated in accordance with the
aforementioned assembly 22 can be provided by any waveform
generating circuitry which can provide time varying waveforms, e.g.
triangular or sawtooth type waveforms, at the fundamental
frequencies required for each open string tone and the required
incremental frequencies for each fret tone. In its preferred
embodiment, the basic frequencies are generated in the subject
invention by six relaxation oscillator circuits 92.sub.1, 92.sub.2,
92.sub.3, 92.sub.4, 92.sub.5 and 92.sub.6, which are identical
insofar as circuit configuration is concerned but the relative
frequency determining values of the components differ. Accordingly,
only one of the oscillator circuits 92.sub.1 is shown in detail and
is configured basically about a programmable unijunction transistor
94, n-p-n junction transistor 95 and a plurality of fret-key
switches 16.sub.1, 16.sub.2 . . . 16.sub.n-1 and 16.sub.n which are
used to select desired increments of resistances 96.sub.1, 96.sub.2
. . . 96.sub.n-1 and 96.sub.n to form a specific RC time constant
with the fixed capacitor 98 to control the oscillator frequency.
Smaller frequency changes are made by a variable resistance element
100 which is utilized for simulated string "tuning" purposes. The
design parameters for this type of oscillator circuit are well
defined in any typical programmable unijunction transistor
manufacturer's brochure, e.g. G.E. application notes AN60-20 dated
1/71 at page 4 and AN90-93 dated 1/72 at page 12. The
programmability feature of this type of circuit is well known to
have been used as a means of organ tone generation. The fundamental
or "open string" frequency of the oscillator circuit 92.sub.1 is
obtained when a fixed supply potential V.sub.1 appearing at
terminal 102 and coupled to circuit junction 104 is applied to
circuit junction 106 common to capacitor 98 through the total
series combination of resistances 96.sub.1 . . . 96.sub.n which
occurs when all of the fret-switches 16.sub.1 . . . 16.sub.n are in
their open condition. When the upper fret-switch 16.sub.1 is
closed, the voltage V.sub.1 appearing at junction 104 is applied at
junction 108, excluding the upper resistor 96.sub.1 from the RC
time constant to thereby produce the next higher tone frequency.
Therefore, eliminating each additional resistor 96.sub.2, 96.sub.3,
etc. in succession results in incrementally higher toner changes
for successively higher fret positions. With this configuration,
depressing one or more fret key 16 of the same set will produce the
tone only of the highest fret key 16.sub.n depressed. In summary,
the function of the fingerboard key switches is to apply the
voltage V.sub.1 to the resistor termination which will produce the
desired tone.
The output of the programmable unijunction oscillator 92.sub.1
which appears at junction 106 is coupled to a respective class C
type modulating output amplifier circuit 108.sub.1 which includes
transistor 110. The purpose of the modulation amplifier 108.sub.1
is to receive a variable frequency audio tone signal having a
constant amplitude or envelope from the audio frequency oscillator
voice" 1, reshape it to a form which contains enriched harmonics,
amplify the new tone signal, and then modulate the signal envelope
to simulate the desired sound or "voice of the musical instrument
being simulated. The output of the oscillator 92.sub.1 is fed to
the base of the transistor 110 by means of resistor 112 and
coupling capacitor 114. Reshaping is provided by the base bias for
class C operation provided by a network consisting of resistors 116
and 118 and the variable resistance 120 coupled back to the supply
potential V.sub.1. The variable resistance 120 is adapted to be
mechanically coupled to the control knob 32 shown in FIG. 1. When
the variable resistor 120 is adjusted for zero resistance and the
actuator 24.sub.1, for example is deflected, an audio tone signal
comprised of narrow low duty cycle rectangular pulses is produced
at the collector junction 122 of transistor 110 which is very rich
in both odd and even harmonics. If the resistance 120 is varied to
provide an increasing resistance, the pulse-width of the tone
signal will increase up to a maximum duty cycle of 50% or less,
thereby approaching a square wave, which is less rich in harmonics
than a narrow rectangular pulse, containing only the odd harmonics.
By this means the harmonic content of the output waveform or the
"timbre" of the voice signal appearing at junction 122 is made
variable. The net effect of this harmonic control achieved by means
of varying the resistance 120 is to provide a wide range of
instrumental voices and pleasing sound effects when desired by the
musician without resorting to extraneous electronic circuits.
It should be pointed out, however, that no audio output will be
produced until such time that the actuator 24.sub.1 closes one or
more of the switch contact elements 58.sub.a . . . 58.sub.d or
62.sub.a . . . 62.sub.d to couple a supply potential V.sub.2 from
terminal 121 to the collector circuit of transistor 110. This
supply potential is provided from the fixed DC source 126 via the
switch 128 and resistor 129 or when desired from an external
source, not shown, coupled to the connector 127. Deflecting the
actuator 24.sub.1 in either direction produces a pulsed or
sustained output waveform envelope of the audio frequency as
desired by the musician depending upon whether the actuator is
momentarily deflected or held in a deflected position. Instrument
"voice" modulation, however, is provided by the network 130 which
is a compensated balanced bridge attenuator network and the manner
in which the actuator 24.sub.1 is moved. If the musician simply
picked the actuator 24.sub.1 so that it is allowed to spring back
like a string, a sound like a plucked string will be produced;
however, if he deflects and holds the actuator 24.sub.1 in a
deflected position, he can sustain the tone to produce tones like
an organ or other tone substaining instruments, including "viol"
types. The amplitude of the modulating waveform and therefore the
sound volume is varied by the amount of deflection of the actuator
24.sub.1. As shown, three amplitude levels are available to the
musician for sound volume expression purposes and they are
proportional to the amount of deflection analogous to deflecting a
musical string.
When the actuator 24.sub.1 is deflected to close the first contact
pair 58.sub.a and 58.sub.b, for example, or 62.sub.a and 62.sub.b,
a step input voltage V.sub.2 is applied to circuit junction 132 of
the compensated attenuator network 130 comprised of resistors 134
and 136 and capacitors 138 and 140. This type of circuit is
disclosed, for example, in the publication entitled "Pulse, Digital
and Switching Waveforms", Millman and Taub, published by McGraw
Hill, 1965, at pp. 50-54. By this means a fast rising voltage pulse
derived from the supply voltage V.sub.2 occurs at circuit junction
142 which is coupled to the collector of transistor 110 via
collector load resistor 144 and forms an abrupt leading edge
"attack" portion of the modulating waveform and to charge the decay
time storage capacitor 146. In the process, the attenuator
capacitors 138 and 140 are also charged from the supply potential
V.sub.2. Upon release of the actuator 24.sub.1, the voltage source
V.sub.2 is cut off. Therefore, the only voltage remaining is
supplied by one or more charged capacitors 138, 140 and 146. These
capacitors discharge to ground 148 through the collector to emitter
circuit of transistor 110 via the collector load resistor 144.
In doing so, a decaying envelope of the oscillator 92.sub.1
frequency appears at the collector junction 122 which closely
simulates the gradually dampened waveform produced by the sound of
a plucked string instrument. If on the other hand the actuator
24.sub.1 is held to keep one or more of its associated switch
contacts closed, the voltage V.sub.2 will be maintained and an
output tone will be sustained for so long as it is held in the
deflected position. Also after any sustained effect is terminated,
the gradually dampened edge of the waveform will be produced by one
or more of the discharging capacitors 138, 140 and 146. It should
be noted also that a muting switch, not shown, can be used to
curtail the decaying trailing edge when desired by the musician.
Such a device, for example, would be a shorting switch for
instantly discharging all three capacitors 138, 140 and 146 to
ground. The switch actuator for such a device would be the muting
pad actuator 38 shown in FIG. 1.
The modulating pulse generating used to simulate the sound of a
plucked string for a stringless guitar-like instrument had in the
past been a fixed wave shape and any changes in the wave shape when
provisions were included had to be preset. As illustrated in the
foregoing description, the pulse waveform generated by the subject
invention can be varied in pulsewidth and/or amplitude purely as a
function of the picking, plucking or strumming action of the
actuators 24.sub.1, 24.sub.2, etc. by a musician. This versatility
is made possible by providing for a fast rising leading edge
(attack) for the amplitude modulating pulse of the voltage V.sub.2
immediately upon the initial deflection of the actuator rather than
after it is released as is customary.
As noted above, the fast rising leading edge required to simulate
the percussive sound of a plucked string instrument is produced by
the network 130 consisting of the bridge formed by resistors 134,
136 and capacitors 138 and 140 connected to the resistor 144 and
capacitor 146. When the actuator 24.sub.1 is deflected slightly to
close its first pair of switch contacts 58.sub.a and 58.sub.b, for
example, an impulse current is produced at junction 142 when a step
voltage input V.sub.2 is applied to the circuit junction 132. Under
these conditions, capacitors 138 and 140 behave like short circuits
such that the rise time of the step voltage appearing at circuit
junction 132 is very nearly reproduced at circuit junction 142
while the final value voltage is attenuated by two stages of a
simple passive resistive network made up of resistors 134 and 136.
When the actuator 24.sub.1 is deflected further until the next
contact 58.sub.c, for example is closed, the voltage V.sub.2 is
applied at circuit junction 150. At this point only one stage of
resistive attenuation provided by resistor 136 remains ahead of
circuit junction 142. Therefore, the amplitude of the signal at
junction 142 is greater than when the voltage V.sub.2 is applied to
circuit junction 132, the result being an increase in sound volume.
It can be seen then that when the actuator 24.sub.1 is deflected so
that the third contact 58.sub.d is closed, the voltage source
V.sub.2 is applied directly to circuit junction 142 with no
attenuation. For this case, the amplitude of the output signal and
therefore the volume of the sound produced at the collector
junction 122 will be at its maximum value.
Accordingly, the compensated balanced bridge attenuator network 130
is adapted to provide leading edge conditioning (attack) for the
modulation envelope as well as the trailing edge conditioning
(decay) thereof in response to the selective actuation of the
switch contacts associated with the actuator 24.sub.1. Control of
the envelope amplitude for expressive sound volume as well as
envelope width extension for control of sustained effects is thus
provided. It should be pointed out that variations of the circuit
configurations can readily be made to provide additional control of
the functions described such as modulation envelope attack and
decay time variations or additional special effects such as
vibrato, etc. without departing from the spirit and scope of the
invention. The output of the modulation amplifier 108.sub.1 as well
as the other five amplifiers 108.sub.2 . . . 108.sub.6 are coupled
in parallel to a common summing junction point 152 by means of the
summing resistors 154.sub.1 . . . 154.sub.6. The common circuit
junction 152 is coupled to an output jack 156 by means of a volume
control potentiometer 158 which is adapted to be mechanically
coupled to the control knob 34 shown in FIG. 1 and a variable RC
tone control circuit including capacitor 160 and a variable
resistor 162 which is adapted to be connected to the control knob
30 also shown in FIG. 1.
When desirable, the on/off switch 128 can be made an integral part
of the volume control potentiometer 158 coupled to the knob 34
shown in FIG. 1. Additionally, a zener diode 166 as shown in FIG. 9
is utilized to provide a stable voltage reference for the supply
potential V.sub.1 which is required for the oscillator circuitry
92.sub.1 . . . 92.sub.6 as well as for the variable resistor 120
utilized in the biasing circuitry for the transistor 110, for
example. The other source voltage V.sub.2 may vary due to different
types of DC supply means coupled to the input power connector 127
or because of a partially discharged battery 126. Accordingly, the
supply potential V.sub.2 is used only for functions that are
relatively insensitive to voltage variations such as capacitor
charging amplitude modulation and sound amplification, etc. The
remainder of the power supply circuitry includes a current limiting
resistor 168, two filter capacitors 170 and 172. As noted above and
as shown in FIG. 1, the indicator light 36 which may be, for
example, a light emitting diode, may be used as a visual indicator
of power status. It can be applied to indicate a power on/off
status or a low battery condition, depending upon the desires of
the user. Also a miniature battery condition meter may be used in
place of the indicator light as desired.
In conclusion then, respective oscillators and modulation
amplifiers are associated with each flexible actuator and a group
of leaf type switches actuated thereby are summed at the junction
152 by means of the six summing resistors 154.sub.1 . . . 154.sub.6
and coupled to the output jack 156. This output can then be
amplified as desired by an amplifier within the body of the
instrument with or without a built-in speaker or it can be
amplified by an external musical instrument amplifier and speaker
system. Typically the output jack 156 is intended to be connected
to a standard electrically amplified guitar-type musical instrument
amplifier or equivalent. If on the other hand the present invention
is configured as a viol type instrument, the signal output would be
coupled to a suitable musical instrument amplifier associated with
such type of apparatus.
While the subject invention has been shown and described with a
certain degree of particularity, it is not desired that the present
disclosure be interpreted in a limiting sense, since it is desired
that all modifications, alterations and variations coming within
the spirit and scope of the present invention are meant to be
included.
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