U.S. patent number 3,591,699 [Application Number 04/716,964] was granted by the patent office on 1971-07-06 for music voicing circuit deriving an input from a conventional musical instrument and providing voiced musical tones utilizing the fundamental tones from the conventional musical instrument.
Invention is credited to Royce L. Cutler.
United States Patent |
3,591,699 |
Cutler |
July 6, 1971 |
MUSIC VOICING CIRCUIT DERIVING AN INPUT FROM A CONVENTIONAL MUSICAL
INSTRUMENT AND PROVIDING VOICED MUSICAL TONES UTILIZING THE
FUNDAMENTAL TONES FROM THE CONVENTIONAL MUSICAL INSTRUMENT
Abstract
A voicing circuit for use with a conventional musical
instrument. A tone pickup is placed on a conventional instrument.
For example, a single coil is placed beneath each string on a
guitar. The signal formed is the fundamental colored with many
harmonics. An electronic circuit filters the harmonics to leave a
much cleaner fundamental. The fundamental is voiced by a voicing
circuit to add harmonics in such portions as to achieve a desired
voicing. The voiced output follows the conventional instrument in
terms of relative volume, shift in fundamental, vibrato of the
fundamental.
Inventors: |
Cutler; Royce L. (Houston,
TX) |
Family
ID: |
24880160 |
Appl.
No.: |
04/716,964 |
Filed: |
March 28, 1968 |
Current U.S.
Class: |
84/736; 84/723;
84/738; 984/367 |
Current CPC
Class: |
G10H
3/186 (20130101); G10H 2230/235 (20130101); G10H
2230/225 (20130101); G10H 2210/066 (20130101); G10H
2230/115 (20130101) |
Current International
Class: |
G10H
3/00 (20060101); G10H 3/18 (20060101); G10h
001/06 (); G10h 001/00 () |
Field of
Search: |
;84/1.01,1.04,1.06--1.17,1.19--1.24,1.26B,1.26F,1.26FD,1.26G,1.26U |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hirshfield; Milton O.
Assistant Examiner: Witkowski; Stanley J.
Claims
I claim:
1. Electronic musical apparatus for forming musical notes voiced in
a predetermined manner and adapted to be used with a typical
stringed instrument having strings which are selectively shortened
to alter the tone of the instrument, the tone formed by the
instrument including a fundamental and harmonics and which
comprises:
a. first transducer means for forming a signal proportional to an
individual string's vibrations, said means being adapted to be
operably coupled with one string on a typical musical instrument
which forms notes having a fundamental and mix of harmonics of
various phases and amplitudes;
b. second transducer means for forming a signal proportional to a
second individual string's vibrations, said means being adapted to
be operably coupled with a second string of such instrument;
c. positioning means for positioning said first and second
transducer means operably coupled with first and second individual
strings, said means positioning said transducer means at selected
distances from the individual strings and a closer distance from
the strings when the strings are shortened to cause said transducer
means to form a larger signal for notes made on respectively
shortened strings;
d. first filter means connected to said first transducer means;
e. second filter means connected to said second transducer
means;
f. each of said filter means being individually tuned for
attenuating the various harmonics, their respective signals
relative to the fundamental, and each having a rolloff point
approximately equal to or greater than the fundamental frequency of
the respective open strings, and further having a rolloff which
relatively attenuates the harmonics of the notes of shortened
strings in comparison with the fundamental of notes of the
shortened strings, said filter means forming respective output
signals of the relatively filtered fundamentals of the open and
shortened strings; and,
g. voicing means including first and second voicing circuit means
for voicing the fundamentals from said first and second filter
means for selectively forming first and second voiced musical
notes.
2. The invention of claim 1 wherein said last-named circuit means
forms a signal having twice the frequency of the fundamental.
3. The invention of claim 1 wherein said last-named circuit means
forms a signal having half the frequency of the fundamental.
4. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the flute.
5. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the string bass.
6. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the bassoon.
7. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the bass guitar.
8. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the bass clarinet.
9. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the two string bass.
10. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the guitar.
11. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the soprano guitar.
12. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the clarinet.
13. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the oboe.
14. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the horn.
15. The invention of claim 1 wherein said voicing means forms a
signal having the quality of the sitar.
16. The invention of claim 1 wherein said last-named circuit means
forms a square wave signal.
17. The invention of claim 16 wherein the frequency of the square
wave signal is equal to that of the fundamental from the musical
instrument.
18. The invention of claim 16 wherein the frequency of the square
wave signal is equal to half that of the fundamental from the
musical instrument.
19. The invention of claim 16 including an additional circuit means
for limiting the envelope of the square wave signal in a manner to
decay the signal.
20. The invention of claim 19 wherein said additional circuit means
is responsive to the time decay of the musical note sounded on the
musical instrument.
Description
RELATED APPLICATIONS
Applicant has no presently pending related applications.
SUMMARY OF PROBLEM AND SOLUTION
The present invention relates to electronic musical instruments
cooperative with tone sources such as stringed instruments, horns
and even human voices wherein the musical instrument forms a wide
range of musical voices. Voicing to form selected musical effects
and tones involves control of the harmonic content of a fundamental
tone or note; the harmonics are mixed with varied amplitude and
phase characteristics. On using an instrumental source, the source
seldom, if ever, forms a pure fundamental as might be obtained from
a tuning fork. Always, harmonics are mixed with the fundamental
from the source. Further compounding the problem is the fact that
apparently identical musical instruments vary in music quality and
therefore in harmonic content resulting from their construction.
The notes sounded on the same instrument will even vary in harmonic
content when played slightly differently. For instance, a stringed
instrument which is plucked at some point between the bridge and
the nut is likely to vibrate in several different modes. If it is
plucked perfectly vertically to the finger board, the mode of
vibration is different from that when plucked horizontally. In all
cases, the percentage of harmonics varies from note to note and
even varies as a function of time because the harmonics die away at
different rates. Even with an open string, plucking the string at
different angles and at different locations along its length will
vary the harmonic mixture at all times after the note is sounded.
With these factors in view, it will be appreciated that the phase
angles, amplitudes, durations and time functions of harmonics vary
in an unpredictable manner. This is true of all stringed
instruments, whether plucked or bowed, and is likewise applicable
to a great degree in all instrumental or tone sources including the
human voice.
Since electronic voicing adds harmonics to a fundamental tone to
derive a musical note of a desired quality, accurate foreknowledge
of the harmonics derived from the tone source is very helpful. If
the fundamental source is a clean sine wave (a tuning fork), this
foreknowledge is accommodated by the voicing apparatus. However,
clean tone sources are simply difficult to obtain from musical
instruments. In the use of musical instruments, the requirements
for a clean (sine) tone source are contradictory of the very nature
of musical instruments since all musical instruments having any
quality whatsoever incorporate a variable mix of harmonics.
In dealing with the problem of harmonic foreknowledge, attempts
have been made in the prior art as might be noted by way of example
hereinafter. For instance, the U.S. Pat. to White bearing No.
3,006,228, discloses a plurality of frequency dividers responsive
to an input signal of mixed frequencies. The dividers from sine
waves which are mixed by gates switched off and on. Further, the
U.S. Patents to Cookerly, et al., bearing Nos. 3,325,579 and
3,213,180 illustrate modification of a conventional instrument to
eliminate harmonics in the various tones. Likewise, a specially
modified conventional stringed instrument is shown in the U.S. Pat.
to Fender, et al., bearing No. 2,455,575.
In some devices of the prior art, no provision whatsoever is made
for the variations in harmonic content so that the voicing of the
input signal from the instrument does not control the musical
quality of the output tone. By way of example, U.S. Pat. No.
3,213,180 discloses a circuit in which harmonics from the source
mixed with the fundamental are merely fed through to the output.
The patents indicate the failure of the prior art in providing a
means for adapting a conventional and unmodified stringed
instrument, horn, or the like for use as a tone source cooperative
with voicing means. Because of the failure of the prior art, there
is presently not available electronic musical instruments operated
from a conventional tone source such as a stringed or wind
instrument which provides suitable voicing to simulate a wide
variety of musical instrument tones and the like. With this in
view, the present invention is summarized as providing individual
pickup means adapted to be positioned beneath single strings of an
instrument for detecting the complex signal therefrom and providing
a clean fundamental; said means further including voicing for 4, 8
and 16 foot pitches with flute or bright tones for instruments such
as the flute, two string bass, bassoon, bass guitar, bass clarinet,
soprano guitar, clarinet, oboe, horn, sitar, and the like.
One object of the present invention is to provide musical
instrument apparatus voicing a tone from a conventional, unmodified
instrument.
Another object of the present invention is to provide a new and
improved means reducing harmonic content of a tone to yield an
essentially clean fundamental.
A related object is to provide a new and improved circuit means
voicing the sitar.
Yet another object of the present invention is to provide a means
cooperative with a shortened string in which the fundamental varies
perhaps two octaves and in which a clean tone essentially free of
harmonics is formed.
A timely object of the present invention is to provide tone pickup
apparatus suitably installed on or removed from conventional string
instruments.
An important object of the present invention is to provide time
decay of the square wave tones to gain quality in tonal
simulation.
Many other objects and advantages of the present invention will
become readily apparent and an understanding thereof will be gained
from a reading of the below included specification and
consideration of drawings, wherein:
FIG. 1 shows a pickup means cooperative with a selected instrument,
typically a guitar, as one tone source suitable for the present
invention;
FIG. 1-A is an enlarged detailed view of the pickup means of FIG.
1;
FIG. 1-B is an enlarged detail view of the pickup means and its
relationship to a string;
FIGS. 2-A, 2-B, and 2-C are frequency response curves of portions
of the circuitry;
FIG. 3 is a schematic wiring diagram of circuitry forming 4, 8 and
16 foot pitches;
FIGS. 4-A and 4-B together illustrate voicing circuitry for use
with the present invention; and,
FIG. 5 illustrates additional voicing means for the present
invention.
In the drawings, attention is first directed to FIG. 1 which
illustrates a guitar bearing the numeral 8. The device of the
present invention will be discussed in cooperation with the guitar
8, although it will be appreciated that other stringed instruments,
horns and selected tone sources are adapted for use with the
present invention. The guitar 8 incorporates a finger board 10
extending on the neck of the guitar to an adjustable means 11 for
controlling the fundamental frequency of a string 12 adjacent the
neck 10. The neck 10 has the frets 13 and a larger fret 15 which
limits the length of the string 12. The string 12 passes over a
bridge 14 at the upper end of the guitar 8. The string 12 is
plucked near its center portions and vibrates from the lower fret
15 to the bridge 14. If fingered, the length of the vibrating
string is determined by the particular fret 13 at which the
instrument is fingered. Because the fingered string is shorter than
the open string, the fundamental has a higher frequency.
In the conventional use of the guitar 8, or any other instrument
for that matter, the string is plucked, bowed or otherwise vibrated
along its free length ending at the bridge 14. The motion of
vibration is definitely complex, always including a fundamental and
perhaps eight or more harmonics of significant amplitude. The
relative amplitudes of the harmonics vary depending on the point at
which the string is plucked. For instance, if the string is plucked
at its exact midpoint, this will tend to suppress or reduce the
amplitude of the even numbered harmonics; however, they will not be
diminished to zero. Moreover, because it is impossible to fabricate
a totally rigid structure at the two end points of the string
including the bridge 14 and the large fret 15, the vibrations
coupled through the instrument to the bridge and large fret alter
the harmonic amplitude and phase in a manner to sound notes which
are a function of elapsed time in the vibrating string. While the
foregoing is not to criticize any instrument and moreover describes
the varied characteristics that give each instrument its unique and
often beautiful voicing, the above difficulties are noted because
the harmonics added in voicing must be controlled as taught by the
present invention.
The numeral 16 indicates a pickup means attached to the musical
instrument 8. The means 16 is enlarged in FIG. 1-A which
illustrates a mounting block 17 temporarily secured to the body of
the guitar and which is adapted to support the various pickup coils
as will be described. A single coil 18 is shown in FIG. 1-A and
preferably incorporates a suitable bobbin having a number of turns
wound thereabout wherein the signal is conducted to circuitry to be
described by a pair of conductors 19. The coil 18 surrounds an
inductor core 20 which is preferably magnetized and responsive to
the string 12 positioned thereabove. In the preferred arrangement,
the core 20 communicates magnetic flux variations to the coil 18 as
the string 12 vibrates. When the string 12 is moved in near
proximity to the core 20, the magnetic circuit is altered to vary
the signal induced in the core 18. When the string moves back and
forth above the upper face of the core 20, a suitable signal is
induced in the coil 18.
Since movement of the string 12 above the core 20 is governed by
the fundamental and harmonics heard from the string 12, the string
12 induces the tones in the coil 18.
The core 20 is sensitive to the string 12 and not to the adjacent
strings of the instrument 8. In the preferred embodiment, the
distance between the core 20 and the string 12 is preferably about
one-sixteenth inch, perhaps one thirty-second of an inch. This does
not interfere with the movement of the string since its range of
movement at or near the bridge is not great enough to touch the
core 20. With the spacing above-described, signals of magnitude are
not detected from adjacent strings. A single pickup coil is adapted
to be positioned beneath each string in the mounting means 17 shown
in FIG. 1-A to thereby provide specially tailored pickups for each
and every string. Thus, if the instrument includes six strings,
preferably six pickups are individually placed across the span of
strings with a magnetic core positioned immediately beneath each of
the strings. A greater number of strings requires the use of
additional pickups, again preferably one pickup per string.
While the foregoing describes installation of the pickup means with
a stringed instrument, the present apparatus is adaptable for other
types of pickups. For instance, a conventional microphone may be
used in lieu of the magnetic induction coil means shown in FIG.
1-A. Other known vibration pickups can be attached to horns,
percussion instruments and the like, and conventional microphones
can even be used with the human voice. Suffice it to say, the
foregoing description is directed to the preferred embodiment of
the stringed instrument pickup as will be described in detail
hereinafter.
Attention is next directed to FIG. 3 of the drawings where the
conductors from the magnetic pickup are indicated by the numeral
19. One side is grounded and the other conductor is communicated
through a suitable coupling capacitor 24 to the base of the
transistor 25. The transistor stage provides amplification wherein
an output signal is developed across a collector resistor 26. The
transistor incorporates a conventional emitter resistor 27 which is
grounded and the base has suitable bias through a resistor 28. The
amplified signal is applied to series resistors 29 and 30 and
partially grounded through a capacitor 31. These circuit
components, in cooperation with a capacitor 32, form a low-pass
filter. The component values are selected so that the open string
fundamental has a frequency signal to or somewhat higher than the
break point in the filter curve at which higher frequencies are
attenuated. That is to say, the fundamental frequency of the open
string, the lowest frequency formed by the individual string 12, is
made equal to or slightly greater than the frequency at which the
output of the filter begins to attenuate the harmonics. Attention
is directed to FIG. 2-A which illustrates the filter
characteristics as a function of frequency.
The filter circuit described above is communicated with a
transistor 34 which operates as an emitter follower with the output
signal developed across the emitter resistor 35. The output signal
is communicated through a series resistor 36 to a tank circuit
comprised of capacitor 37 and an inductor 38. Preferably, the tank
circuit is tuned to its optimum impedance at the fundamental
frequency of the open string. Higher frequencies from the string
are thusly attenuated quite rapidly with increase in frequency. The
Q of the tank circuit need not be excessively high, but should be
substantial to yield the characteristics shown in FIG. 2-B.
The transfer function of the tank circuit described above and the
low-pass filter proceeding it should be considered. On plucking the
open string 12, the fundamental frequency is the lowest possible
tone derived from the string 12. The low-pass filter and the tank
circuit together cooperate to slightly attenuate this fundamental.
However, all harmonics of the open string are substantially
attenuated so that the output signal from the tank circuit is an
essentially clean sine wave. In a typical example, the second
harmonic on the string 12 may have an amplitude equal to 50 percent
or more of the fundamental. By using the circuitry described above,
the second harmonic is substantially eliminated on reduction of the
signal by several db. compared with the fundamental. FIG. 2-C shows
the combined characteristics of the two circuits. Third, fourth and
additional harmonics are even further reduced.
The effects on the fundamental and various harmonics of the filter
and tank circuit for tones derived from a shortened string 12. When
the string is shortened by fingering the frets 13, the fundamental
of the shortened string is substantially higher in tone. On the
composite response curve of the low-pass filter and the tank
circuit in FIG. 2-C, the fundamental is thusly attenuated. However,
the harmonics of the higher fundamental are substantially
attenuated so that a relative reduction on the order of several
db.'s is still obtained. Moreover, the absolute amplitude of the
fundamental tone derived from the shortened string compares
favorably with the amplitude of the fundamental of the open string,
in spite of attenuation of the tank circuit and the low-pass filter
as shown in FIG. 2-B. The reason for this is the fact that the
string 12 is brought ever closer to the magnetic coupling means 20
when the string is fingered. Since the coupling is a square law
function, the smaller fundamental vibrations on the shortened
string are still detected with sufficient amplitude by the pickup
means and the attenuated output signal from the tank circuit is
quite ample.
Resuming consideration of the amplifier circuitry in FIG. 3, the
tank circuit provides an input signal to the capacitor 40 for the
base of the transistor 41. The transistor has a conventional load
resistor 42 and two emitter resistors 43 and 39. The connection of
the resistor 39 is such to provide a volumn control.
An output resistor 44 communicates the amplified signal to
additional circuitry as will be described, the signal being best
described as the 8 foot pitch, a sine wave.
Reviewing the circuitry means mentioned hereinbefore, each of the
strings of the instrument 8 forms a fundamental tone which is
varied on fingering or shortening the string. As noted before, the
fundamental is mixed with numerous harmonics; the circuitry
described above substantially eliminates the harmonics to form the
8 foot pitch which is an essentially clean sine wave. The
application of the sine wave to form other wave forms will be
described hereinafter, and reference is made to the voicing
circuitry as will be described also.
A coupling capacitor 45 communicates the 8 foot pitch to a
transistor 46. The base voltage of the transistor is determined by
a voltage divider including resistors 47 and 48. The transistor 46
is a phase splitter and for this reason, has equal value collector
and emitter resistors 49 and 50. Coupling capacitors 51 and 52
communicate the opposite phase signals to a pair of rectifying
diodes 53 and 54. The anode potentials of the diodes are determined
by a resistive network including equal resistors 55 and 56. The
resistors 55 and 56 are tied to a selected point on a voltage
divider incorporating series resistors 57 and 58. The rectified
positive pulses from the diodes 53 and 54 develop a wave form
across a grounded resistor 59. The 4 foot pitch signal is output
through a resistor 60.
The phase splitter 46 forms out of phase signals at the 8 foot
pitch. The diodes 53 and 54 pass only the positive half-cycles of
wave form presented to each of the diodes which are then summed
across the resistor 59. The summation provides the 4 foot pitch, at
a frequency twice that of the 8 foot pitch. The function and use of
the 4 foot pitch will be thoroughly described hereinafter.
Attention is next directed to a resistor 64 which communicates the
8 foot pitch to a capacitor 65. The coupling capacitor 65 is tied
to a grounded diode 66 which permits passage of only the positive
half-wave pulses to the base of a transistor 67. The transistor 67
includes a conventional collector resistor 68 and suitable base
bias is provided by a resistor 69. A coupling capacitor 70 derives
an overdriven sine wave signal from the transistor 67, an almost
squared wave form. The transistor 67 inverts the wave form which is
then communicated to additional circuitry to complete squaring of
the sinusoidal wave form. The signal is developed across a grounded
resistor 71 and the signal is communicated through a diode 72 which
is input to the base of a transistor 73. The base voltage is
controlled by a resistor 74 tied to the B+ supply line. The squared
signal is developed across a collector load resistor 75. More will
be noted concerning the use of the square wave from the
above-described circuitry having a frequency to that of the 8 foot
pitch.
A conductor 77 communicates a squared wave to a diode 78. More will
be noted concerning the diode 78 hereinafter. Also, the conductor
77 is connected to a flip-flop 80. It is believed unnecessary to
identify every circuit component of the flip-flop divider 80 since
the circuit is well known in the art. It is significant to note
that the signal on the conductor 77 is at the 8 foot pitch. The
flip-flop 80 forms a square wave at half the frequency, or at the
16 foot pitch. The conductor 77 is input to the flip-flop 80 to
actuate the flip-flop 80 with the 8 foot pitch. The output signal
is derived on a conductor 81 which communicates with a diode 82
which will be described in conjunction with operation of the diode
78 hereinafter.
Attention is redirected to the 4 foot pitch formed at the phase
splitter transistor 46. While one output is derived through the
coupling resistor 60, an additional output is derived through a
resistor 84 input to the base of a transistor 85. The transistor
operation point is controlled by base voltage resistors 86 and 87.
The degree of amplification of the transistor 85 is controlled by
the variable emitter resistor 88 while the output signal is
developed across a collector resistor 89. The polarity of the
output signal should be noted. The rectifying diodes 53 and 54 form
a positive input level to the base of the transistor 85. The signal
is inverted by the transistor 85. High frequency components of the
output signal are grounded by a capacitor 90 wherein the DC
component of the amplified signal is input to a transistor 92
through a base resistor 93. Utilizing a PNP transistor to invert
the wave form from the NPN transistor 85, the amplified signal from
the transistor 92 is developed across the collector load resistor
94 and again high frequency components of the signal are grounded
by a capacitor 95. The emitter of the transistor is connected to
the supply line by a resistor 96. The output wave form is developed
at the collector of the transistor 92. The base signal turns the
transistor on rather strongly when a musical note is first sounded
to switch the transistor from a nonconducting state to a heavy
conducting state. This increases the voltage drop across the
resistor 94 from approximately ground potential to perhaps one-half
the supply line potential. Since the transistor 92 provides a DC
level representing the average of the tone derived from the musical
instrument 8 for a sounded note, the amplitude builds quickly to a
peak and decays for an interval of time. Likewise, the signal from
the transistor 92 rises quickly to a peak value and decays during
the same interval. This output signal is derived from the collector
of the transistor and is used in the following manner.
The collector signal is communicated by way of resistors 96 and 97
to the anodes of the diodes 78 and 82 previously noted. The voltage
wave form serves as a limiting envelope on the square waves passed
by the diodes 78 and 82 to form a suitable wave form which decays
in the proper manner. The diode 78 is connected to a resistor 98 to
provide the needed output signal. Likewise, the diode 82 provides
an output signal through a resistor 99 which is limited in envelope
by the signal through the resistor 97. For convenience, the two
signals are respectively called the 8 foot and 16 foot square
waves.
Attention is next directed to FIGS. 4-A and 4-B of the drawings. In
FIG. 4-B, the numeral 100 refers generally to the amplifier means
of the present device which suitably matches the various voiced
tones with an output amplifier of conventional construction for an
output speaker. The function of the amplifier 100 will be noted in
detail hereinafter after description of the voicing circuitry
proper, the treble tone being generally synthesized by circuitry in
FIG. 5 and the bass tones being provided by the circuitry in FIG.
4-A. The numeral 110 indicates the voicing generally. First, the
numeral 111 indicates a conductor from the treble tones while the
numeral 112 indicates a conductor input from the bass tones. Should
the device of the present invention be incorporated with a guitar
having the standard six strings, musical nomenclature has
identified the two larger strings as the bass strings while the
remainder of the strings are grouped as the treble tones. Should
the device of the present invention be used with something other
than the guitar, one will note in many instruments a division of
the keyboard or fingering such that bass and treble grouping of the
tones is customary. For the guitar, and in accordance with the
discussion hereinbefore, the circuit means 22 of FIG. 3 is
duplicated for each string, and each tone pickup 16 previously
described. Again, using the guitar only as an example, the four
treble strings are communicated with a circuit means 22 and each of
the four circuit means is output through the resistor 44 (see FIG.
3) which provides the 8 foot pitch to the conductor 111. In like
manner, the conductor 112 is connected to the various base tone
circuits to derive the 8 foot pitch also.
Considering first the common circuitry, the numeral 113 indicates a
conductor which provides a positive voltage to switching for
turning off and on the various voicing circuits to be described.
The numeral 114 indicates a conductor from a negative power supply
and preferably, the negative and positive supply lines are equal
levels relative to ground potential. The numeral 115 indicates the
conductor on which the voiced signals are summed for input to the
amplifier 100, the conductor 115 communicating with the circuitry
of FIG. 5 which includes additional voicing circuitry. The
conductor 117 communicates with a suitable voltage adjusted by a
potentiometer to control the tone of the apparatus. As will be
described, the tone control circuitry tends to ground certain high
frequency signals to change the quality of the signal. The numeral
118 indicates conductor for the 16 foot bass square wave tones,
those tones derived from the lower voiced portion of the stringed
instrument, keyboard or other musical source. Also, the numeral 119
indicates the input conductor from the 16 foot treble square waves
as will be used by the various voicing circuitry.
Considering the circuits illustrated, the conductor 111 is
communicated through a resistor 125 and input to a FET switch 126.
A switch 127, preferably located convenient for the musician,
communicates a positive voltage through a megohm resistor 128 to
the gate of the FET 126. On operation of the switch 127, suitable
bias voltage is applied to the gate to turn the transistor 126 on.
In its conventional operation, it is biased off by a negative
potential applied through a resistor 129 to the gate. To avoid
erratic operation, high frequency signals at the gate are grounded
through a capacitor 130. This leaves the voltage of the base
essentially a DC level changed only on closure of the switch 127.
When the switch is open, the gate is biased off and no signals are
passed. When the switch 127 is closed, the source and drain are
communicated together, thereby inputting the 8 foot pitch tone or
signal to the conductor 115, the common bus for the amplifier
100.
The next voicing to be described is controlled by the switch 134.
The switch means 134 provides voicing for the two string bass as
will be described. The switch 134 provides a biasing signal through
a resistor 135 to a FET switch 136. The FET is biased off by a
resistor 137 connected to the negative voltage source 114. AC
signals at the gate are grounded by a capacitor 138. The conductor
112 is input through a series resistor 139 while the 16 foot bass
square waves are input through a resistor 140. The two inputs are
summed with high frequencies grounded by a capacitor 141. The
summed inputs are communicated through a resistor 142 to the FET
switch 136. When the switch is biased on at the gate, the signals
are communicated to the common bus 115 for the preamplifier means
100.
Attention is next directed to a switch 143 which provides voicing
for the string bass. The switch 143 provides a gate voltage through
a resistor 144 which is input to a FET 145. The FET 145 connects
suitably filtered signals from the conductors 112 and 118 to bus
115. In the quiescent condition, the FET is maintained off by the
negative potential at the gate provided through a resistor 146. AC
signals at the gate are again grounded by a capacitor 147. When the
switch 143 is closed, the FET 145 conducts to communicate the
voiced signals to the amplifier bus 115.
The next instrument to be considered is the bassoon, for which
voicing is provided on closure of the switch 150. The switch 150
applies a suitable bias through a resistor 151 to the gate of a FET
switch 152. The FET switch is maintained in the off condition by
the voltage applied to the gate through a resistor 153 which is
connected to the negative supply line 114. Quality of the bias
potential is maintained by the grounded capacitor 154. The bassoon
signal is obtained from the 16 foot treble tones on the conductor
119. The bassoon voicing includes the following circuit elements. A
double-tee filter including resistors 154a, 155, 156, 157 and 158
is input to the FET 152. One leg of the filter incorporates a
grounded capacitor 159 which provides some forward phase shift. The
other leg of the filter incorporates a grounded capacitor 160 which
likewise provides forward phase shift. This leg further
incorporates a grounded tank circuit including the inductor 161 and
a capacitor 162. The characteristic sound of the bassoon is
particularly aided by the resonant circuit which yields the
pulsating sound characteristic of the woodwind.
The bass guitar is simulated on closure of a switch 166. Closure of
the switch 166 communicates on a level through a resistor 167 which
is applied to a FET 168. In the normal condition, the FET is
maintained off by a resistor 169 which is returned to a negative
supply. Again, the gate is grounded by a capacitor 170 to remove AC
signals from the gate. The bass guitar is obtained from the 16 foot
tones on the conductor 119. Suitable high frequency grounding is
provided by the circuitry which incorporates series resistors 171,
172, and 173, and high frequency grounding capacitors 174 and
175.
The numeral 177 indicates the switch which provides voicing for the
bass clarinet. The switch 177 operates through a resistor 178 to
switch off and on a FET switch 179. The FET 179 is normally
maintained off by a resistor 180 connected to the negative supply
line 114. AC signals at the base are grounded by a capacitor 181.
The input to the FET 179 is from the conductor 119 again. The
conductor 119 is input to series resistors 182 and 183. Some AC
grounding is provided by a capacitor 184. The grounding is not as
substantial as that provided by the capacitors 174 and 175 in the
bass guitar, it being appreciated that the bass clarinet includes a
richer portion of high frequency tones.
The above tones are input to the conductor 115 for the preamplifier
means 100. The conductor 117 for the tone control means responds to
a suitable voltage at a control convenient for the musician and is
input through the base of a transistor 188. The base incorporates a
series resistor 187. The transistor 188 is used as a switch to vary
the quantity of the capacitor 189 connected between the signal
conductor 115 and ground. AC signals at the base of the transistor
188 are grounded by a capacitor 190. When the transistor is
switched off, the capacitor 189 provides no conduction to ground.
However, when the transistor 188 conducts, it serves as a switch in
a varying degree controlled by the base signal whereby the
capacitor 189 is partially or even completely grounded. As this is
controlled, the quantity or measure of high frequency signals
grounded by the transistor circuitry is also varied.
Continuing on with FIG. 4b to complete the amplifier means 100,
attention is next directed to the input capacitor 200 of the
amplifier means 100. An emitter follower transistor 201 has a
suitable bias from a voltage divider including resistors 202 and
203. The output signal is developed across an emitter resistor 204.
The output signals are coupled through a blocking capacitor 205 to
additional circuitry. The next stage of the amplifier incorporates
an amplifying transistor 206. Base voltage is determined by a
resistor 207 returned to the collector, and the transistor includes
conventional collector resistor 208 and emitter resistor 209. The
output signal is developed across the collector load resistor 208
and emitter resistor 209. The output signal is developed across the
collector load resistor 208 and is coupled by a capacitor 210 to
additional circuitry.
Volume control of the preamplifier means 100 is provided at a
conventional rheostat convenient to the musician. Viewing the
circuitry again, the resistors 211 and 212 provide slight grounding
of the signal in parallel with a resistor 213. The resistor 213 is
grounded under control of a transistor 214. The transistor 214
obtains its base voltage through a series resistor 215 which is
communicated with a variable voltage source on a conductor 216
communicating from the volume control of the musician. As the
musician selects a suitable base voltage for the transistor 214,
the degree that the transistor is turned off or on varies the
resistance in the circuit. AC hum is prevented by a capacitor 217
which is grounded at the base of the transistor 214.
A coupling capacitor 220 transfers the signal after the volume has
been adjusted, and further amplification is obtained from a
transistor amplifier 222. The amplifier 222 incorporates a base to
collector resistor 221 in the megohm range. The transistor has a
conventional collector resistor 223 and grounded emitter resistor
224. The output signals are developed across the collector load
resistor 223. A coupling capacitor 225 provides an audio output
signal on a conductor 226. To prevent charge accumulation on the
capacitor 225, a substantially large resistor 227 is grounded on
the output side at the conductor 226.
While the foregoing describes the preamplifier means 100 from which
the voiced signals (musical tones) are relayed to a suitable
amplifier and speaker system, the conductor 115 shown in FIG. 4A is
also found in FIG. 5 in communication with additional voicing
means. For this purpose, attention is next directed to FIG. 5 for a
description of the additional voicing. The voicing provided in FIG.
5 is denoted as the treble voicing generally, although no
particular classification is intended by this description.
Attention is directed to the input conductors 111, 112, 118 and 119
in FIG. 4A. In addition, the bass and treble division for other
tones is likewise effected in FIG. 5. The numerals 230 and 231
indicate the bass and treble tones, respectively, of the 8 foot
square wave. Likewise, the numerals 232 and 233 indicate the bass
and treble, respectively, 4 foot pitches input to the circuitry
from the various tone generator means 22 described hereinbefore.
Again, it should be emphasized that the bass and treble
designations used herein imply a split keyboard, or other split
voicing as in the guitar 8. With other instruments, the divisions
may vary and may be eliminated as the need may arise.
Considering operation of the circuitry shown in FIG. 5, it will be
noted that the base and treble tones are input to circuit means
adding or merging the two signals. For instance, the conductor 233
is the input for the 4 foot pitch treble tones. The conductor 233
is connected to the source of a FET amplifier 240. The conductor
232, on which the bass tones are derived, is input to the drain of
the same transistor. The transistor 240 is biased off in the normal
condition by connection of a resistor 241 to the negative supply
114. Additionally, a resistor 242 communicates with a switch 243
connected with a positive supply 113 for turning on the FET 240. In
the quiescent condition, the FET is biased substantially off until
closure of the switch 243. When the switch is closed, the channel
conducts to communicate the source and drain. The source and drain
are also connected by way of resistors 244 and 245 to ground.
Similar circuitry is provided for the conductors 111 and 112 on
which the treble and bass 8 foot tones are derived. Attention is
directed to the FET 246 which likewise incorporates the resistors
247 and 248 connected to ground. The FET has a common base
connection with the FET 240 and utilizes the switch 243 in the same
manner.
The conductors 230 and 231 are both input to the FET 250. Again,
the source and drain are communicated to ground by way of resistors
251 and 252. The gate of the FET 250 is common to the gates of the
previously noted transistors and obtains switching voltage in the
same manner. Lastly, the conductors 118 and 119 are input to a FET
254 associated with the resistors 255 and 256. The FET 254
functions in the same manner as those described heretofore, its
gate being common to resistors 241 and 242 which provide the
control voltages. A capacitor 257 grounds high frequency signals
picked up at the gates of the various transistors to prevent
modulation of the switching transistors.
Concerning the voicing illustrated in FIG. 5, attention is first
directed to a FET 264 which serves as a switch to the voicing of
the guitar. A switch 265 connected with a resistor 266 turns on the
FET 264. The FET 264 is normally turned off by connection of a
resistor 267 to a negative supply. Again, AC signals at the base
are grounded by a capacitor 268. The FET 264 sums two inputs, one
of which is derived through a resistor 269 directly to the summed
treble and bass 8 foot pitch tones. The other input is the 4 foot
pitch tones input through the resistor 270, grounded capacitor 272,
and additional resistor 271 which provides some phase shift to the
signal. The transistor 264 is connected to the conductor 115 which
is the signal bus input to the preamplifier means 100 shown
previously in FIG. 4B.
Voicing for a soprano guitar is actuated on closure of a switch
275. The switch provides control voltage through a resistor 276 to
a FET 277. Normally, the FET 277 is turned off by connection of a
resistor 278 to negative supply while again, AC signals at the gate
are grounded by a capacitor 279. The single input to the soprano
guitar voicing circuitry is the 4 foot pitch tones. The input is
derived through series resistors 281 and 282 with a grounded
capacitor 283 providing some roll off with higher frequencies.
Voicing for a clarinet is provided on actuation of a switch 285. A
sufficient voltage for turning on a FET transistor 287 is conveyed
through the resistor 286 to the gate. The gate incorporates
connections through a resistor 288 to a bias source while AC
signals at the gate are grounded by a capacitor 289.
Voicing for the clarinet utilized the 8 foot square wave tones. The
signals are input through series resistors 290 and 291 with some of
the high frequency content of the square waves grounded by a
capacitor 292.
Voicing for the oboe is initiated on closure of a switch 295. The
switch 295 turns on a FET transistor 296 on application of voltage
through a resistor 297 to the gate. The gate is normally turned off
by a resistor 298 connected with a negative supply while AC signals
are grounded by a capacitor 299.
The oboe voicing is derived from the 8 foot square wave, both bass
and treble. The transistor 296 is provided with a summed input
wherein the square wave is communicated through serial resistors
300 and 301. The resistive circuitry inputs the square wave to a
resonant circuit including a capacitor 302 and inductor 303. The
square wave input causes the resonant circuit to ring which adds
the rasping high frequency tones to the square wave input to the
FET 296. The extent of the ringing square wave is reduced by series
resistors 304 and 305 and grounded capacitor 306 which reduce the
ringing amplitude and modify the slope of the square wave input to
the transistor 296. It will be appreciated from the foregoing that
the oboe voicing is derived from the circuitry described.
A switch 310 provides horn voicing whereupon closure biases a FET
312 through a resistor 311. The FET 312 is maintained off by a
resistor 313 connected to a negative supply and high frequency
signals at the gate are grounded by a capacitor 314. Again, the
square wave input is utilized for the voicing of the horn. The
signal is input through the series resistors 315 and 316. Again, a
resonant circuit including a capacitor 319 and an inductor 318 is
connected by way of a resistor 317 to the resistor 316. The ringing
of the resonant circuit adds the quality of the horn to the square
wave.
A switch 325 controls voicing for the sitar. The switch provides a
voltage through a resistor 326 which counteracts the bias resistor
327. The resistors and a capacitor 328 are connected to the gate of
a FET 329. The FET has one input from a resistor 330 connected by a
conductor 331 to the conventional guitar pickup on the instrument.
These devices are well known in the art. A series of resistors 322
and 333 input a square wave to a resonant tank including a
capacitor 334 and an inductor 335. The ringing of the oboe tone
imposed on the electric guitar sound so well known simulates the
sitar in a very realistic manner.
As before stated, all the voiced signals are supplied to the
amplifier means 100 in FIG. 4b. The output is then conducted to the
conventional amplifier and speaker for audio reproduction.
Particular emphasis is placed on control of the harmonic content.
The voicing circuits described herein add consistent harmonic
content to the fundamental, and the problem of an unmeasured and
variable quantity of harmonics in the input is avoided by the
present invention. Moreover, the close control of harmonic content
is achieved even with conventional tone sources, without
modification by a pickup means which is both easily attached and
removed. Thus, the deficiencies of the prior art are cured in that
the voicing is perfectly controlled in the circuitry and is not
irregularly poor because of change in the tone source
harmonics.
Many alterations of this invention are available to one skilled in
the art. Rather than enumerate them, the scope of the present
disclosure is determined by the claims appended hereto.
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