U.S. patent number 3,901,120 [Application Number 05/405,542] was granted by the patent office on 1975-08-26 for electronic tuning device for musical instruments.
Invention is credited to John S. Youngquist.
United States Patent |
3,901,120 |
Youngquist |
August 26, 1975 |
Electronic tuning device for musical instruments
Abstract
A miniaturized electronic device for tuning musical instruments
includes a pick-up microphone and an array of light emitting
diodes. A phase lock loop connected to the microphone locks to the
fundamental, a harmonic or subharmonic of the tone produced by a
musical instrument and produces a corresponding output. A tone
reference generator and associated frequency selector produce a
reference output at a frequency n times that of the fundamental of
the correct tone, there being n display diodes in the array. A
sequencing device connects the two outputs to the display diodes so
that when the tone is sharp the diodes are sequentially energized
in one direction and are sequentially energized in the opposite
direction when the tone is flat. When the tone produced by the
musical instrument is in pitch, a stationary display is produced by
periodic energization of only one of the diodes.
Inventors: |
Youngquist; John S. (Fort Erie,
Ontario, CA) |
Family
ID: |
23604129 |
Appl.
No.: |
05/405,542 |
Filed: |
October 11, 1973 |
Current U.S.
Class: |
84/454; 984/260;
324/76.39 |
Current CPC
Class: |
G10G
7/02 (20130101) |
Current International
Class: |
G10G
7/02 (20060101); G10G 7/00 (20060101); G10G
007/02 () |
Field of
Search: |
;324/78R,78Z,78J,78N,78Q,78E,79R,79D,83R,83A ;84/1.01,454 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hartary; Joseph W.
Assistant Examiner: Weldon; U.
Attorney, Agent or Firm: Bean & Bean
Claims
What is claimed is:
1. An electronic device for tuning musical instruments, comprising
in combination:
periodic display means for visually indicating the relative tune of
a note produced by a musical instrument, said display means
comprising an array of at least three visual indicator devices and
sequence switching means having first and second input terminals
for respectively enabling said visual indicator devices
sequentially in consonance with the frequency of an input signal at
said first input terminal and for energizing that visual display
device enabled by the input signal at said first input terminal in
consonance with coincidence of an input signal at said second
terminal with an input signal at said first input terminal;
transducer means for producing an electrical signal representing
the frequency content of a tone produced by a musical
instrument;
converter means connecting said transducer means to one of said
input terminals for producing a first pulse train output at such
one input terminal whose pulse repetition frequency represents a
component of said frequency content; and
reference generator means connected to the other of said input
terminals for producing a second pulse train output whose pulse
repetition frequency represents the correct tone to be produced by
the musical instrument;
the frequencies of said first and second pulse train outputs being
harmonically related when the tone produced by the musical
instrument is in pitch with respect to said reference generator
means whereby one only of said visual indicator devices is
repetitively energized when the tone is in pitch, said visual
indicator devices are energized sequentially in one direction when
the tone of the musical instrument is sharp, and said visual
indicator devices are energized sequentially in the opposite
direction when the tone is flat.
2. An electronic device for tuning musical instruments as defined
in claim 1 wherein said converter means comprises a phase lock
loop.
3. An electronic device for tuning musical instruments as defined
in claim 2 wherein said reference generator means produces said
second pulse train output signal at a frequency of nf where n is
the number of visual indicator devices and f is the frequency of
the correct tone to which the musical instrument is to be
tuned.
4. An electronic device for tuning musical instruments as defined
in claim 3 wherein said reference generator means comprises a
stable crystal oscillator having a frequency output many times
higher than the frequency range of tuning, counter means driven by
the output of said oscillator, and gate means for producing an
output pulse upon attainment of a predetermined count by said
counter.
5. An electronic device for tuning musical instruments as defined
in claim 4 including means for selectively altering the apparent
count of said counter means whereby to change the pluse repetition
frequency of said second pulse train output.
6. An electronic device for tuning musical instruments as defined
in claim 1 wherein said reference generator means produces said
second pulse train output signal at a frequency of nf where n is
the number of visual indicator devices and f is the frequency of
the correct tone to which the musical instrument is to be
tuned.
7. An electronic device for tuning musical instruments as defined
in claim 6 wherein said reference generator means comprises a
stable crystal oscillator having a frequency output many times
higher than the frequency range of tuning, counter means driven by
the output of said oscillator, and gate means for producing an
output pulse upon attainment of a predetermined count by said
counter.
8. An electronic device for tuning musical instruments as defined
in claim 7 including means for selectively altering the apparent
count of said counter means whereby to change the pulse repetition
frequency of said second pulse train output.
9. An electronic device for tuning musical instruments as defined
in claim 2 wherein said reference generator means comprises a
stable crystal oscillator having a frequency output many times
higher than the frequency range of tuning, counter means driven by
the output of said oscillator, and gate means for producing an
output pulse upon attainment of a predeteremined count by said
counter.
10. An electronic device for tuning musical instruments as defined
in claim 9 including means for selectively altering the apparent
count of said counter means whereby to change the pulse repetition
frequency of said second pulse train output.
11. An electronic device for tuning musical instruments as defined
in claim 1 wherein said reference generator means comprises a
stable crystal oscillator having a frequency output many times
higher than the frequency range of tuning, counter means driven by
the output of said oscillator, and gate means for producing an
output pulse upon attainment of a predetermined count by said
counter.
12. An electronic device for tuning musical instruments as defined
in claim 11 including means for selectively altering the apparent
count of said counter means whereby to change the pulse repetition
frequency of said second pulse train output.
13. An electronic device for tuning musical instruments, comprising
in combination:
transducer means for producing an electrical signal representative
of the frequency content of a tone produced by a musical
instrument;
phase lock loop means connected to said transducer means for
producing a first pulse train output signal which is locked to a
component of said frequency content;
a plurality of light emitting devices arranged in a sequential
array thereof;
reference frequency generator means for producing a second output
pulse train of fixed frequency; and
gating means connected to said generator means and to said first
pulse train output for enabling said light emitting devices
sequentially at the pulse repetition frequency of said second
output pulse train and for energizing a light emitting device upon
coincidence of pulses of said first and second output pulse
trains.
14. An electronic device for tuning musical instruments as defined
in claim 13 wherein the pulse repetition frequency of said second
pulse train output is nf where n is the number of said light
emitting devices and f is the frequency to which the musical
instrument is to be tuned.
15. An electronic device for tuning musical instruments comprising,
in combination:
transducer means for producing an electrical signal representing
the frequency content of a tone produced by a musical
instrument;
converter means connected to said electrical signal for producing a
first pulse train output whose pulse repetition frequency
represents a component of said frequency content;
reference generator means for producing a second pulse train output
whose pulse repetition frequency represents the correct tone to be
produced by the musical instrument and which is related by a
multiplication factor m to the pulse repetition frequency of the
pulse train output first mentioned when said first mentioned pulse
train output corresponds to the correct tone, m being greater than
one;
at least three visual indicator devices arranged in an array;
switching means connected to said second pulse train output for
producing sequential enabling signals corresponding sequentially to
said visual indicator devices, said switching means having at least
three output terminals at which said enabling signals sequentially
appear; and
coincidence means associating each said output terminal with a
different one of said indicating devices and connected to said
first pulse train output for energizing said indicator devices in
consonance with coincidence of said enabling signals and the pulses
of said first pulse train output whereby one only of said visual
indicator devices is repetitively energized when the tone is in
pitch, said visual indicator devices are energized sequentially in
one direction when the tone of the musical instrument is sharp, and
said visual indicator devices are energized sequentially in the
opposite direction when the tone is flat.
16. An electronic tuning device as defined in claim 15 wherein the
pulse repetition frequency of said second output pulse train is nf
where n is the number of indicator devices and f is the frequency
of the tone to which the musical instrument is to be tuned.
17. An electronic tuning device as defined in claim 16 wherein said
converter means comprises a phase lock loop.
Description
BACKGROUND OF THE INVENTION
Various devices have been proposed or utilized in the past for
providing some type of visual display indicative of the state of
tune of a musical instrument. Such devices ordinarily have employed
various mechanical or electro-mechanical devices and have been
relatively large and unwieldy and, as well, require a relatively
large power input. Also, it is usual to require a relatively long
warming up period before such devices have stabilized sufficiently
well to perform their intended function.
It would be desirable, however, to provide a small, portable and
self-sufficient tuning device for musical instruments which could
be switched on or off instantaneously and which could be
immediately used for tuning purposes.
BRIEF SUMMARY OF THE INVENTION
It is, accordingly, of primary concern in connection with the
present invention to provide an electronic device, self-contained
tuning device for musical instruments, and which includes an array
of indicator devices for visually indicating the state of tune of a
musical instrument. The operation of the device is such that the
indicator devices of the array are energized sequentially in one
direction when the tone of an associated musical instrument is
sharp, the display devices are energized sequentially in the
opposite direction when the tone is flat, and wherein a stationary
display is produced when the musical instrument is in pitch, the
stationary display being characterized by the periodic energization
of one of the display devices.
Basically, the circuit according to the present invention embodies
a sequencing means which accepts two inputs, both of pulse train
form, one of which is produced by a pulse generator means and the
other of which is produced by a converter which accepts the
frequency content of the tone produced by the musical instrument.
When the musical instrument is in pitch with the tuning device, the
prfs (pulse repetition frequencies) of the two pulse train outputs
noted are harmonically related such that the aforesaid stationary
display is provided, one of the pulse train outputs sequentially
enabling the individual visual display devices and the other of the
pulse train outputs energizing a selected visual display device
provided that coincidence exists between the two pulse train
outputs.
Preferably, the pulse train output of the pulse generating means is
the nth harmonic of the fundamental tone where n is equal to the
number of display devices.
Of particular importance in connection with the present invention
is the provision of a converter in the aforesaid combination
wherein the converter is in the form of a phase lock loop. This
type of arrangement is especially effective for the purposes
intended inasmuch as it will operate in the presence of substantial
background noise and will operate effectively irrespective of
frequency content of the musical instrument producing the tone
under test. That is to say, the loop can equally as well lock onto
the fundamental, a subharmonic or a harmonic thereof without change
in operation of the device and will therefore accommodate to a
musical instrument whether same produces essentially a fundamental
tone, is enriched in harmonics with suppressed fundamental,
etc.
The pulse generating means according to the present invention is
also of importance in that by programmable coding techniques, a
highly stable crystal oscillator produces the single reference
frequency and dividing techniques are employed to produce,
selectively, the reference pulse train output whose prf pulse
repetition frequency is of the correct frequency for the tone under
consideration.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
FIG. 1 is a perspective view showing a device constructed according
to the present invention and illustrating the general mechanical
layout thereof;
FIG. 2 is a block diagram illustrating in simplified fashion the
basic principles according to the invention;
FIG. 3 is a block diagram illustrating the pulse generator
reference means inclusive of the coding technique employed for
producing the desired output pulse train prf;
FIG. 4 is a block diagram illustrating the principles of the
converter means and of the sequence switching means according to
this invention; and
FIG. 5 is a circuit diagram illustrating a preferred embodiment of
the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring at this time more particularly to FIG. 1, the tuning
device according to the present invention and in its preferred form
will be seen to include a suitable case or housing 12 within which
the battery source of power and the electronic circuitry are housed
and mounting an array of indicator devices 14, 16, 18, 20, 22, 24,
26 and 28. A selectivity control knob 30 is provided as is a tone
selector knob 32 and there is also provided an on-off switch 34. A
suitable receptacle at the side of the casing 12 accepts the jack
36 of a flexible cable 38 to which the pick-up microphone 40 is
attached, substantially as is shown.
According to the objects of this invention, the casing 12 is of
pocket-size dimensions or less and is completely self-contained to
include all of the electronic circuitry and the power source in the
form of a battery or batteries as well.
In operation, the device functions to produce different kinds of
displays at the light producing devices 14-28 which indicate the
state of tune of the musical instrument whose tone is picked up by
the microphone 40. Specifically, when the tone of the instrument is
sharp or flat, the indicator lights or display devices 14-28 will
sequentially glow or be energized either from the left to right as
viewed in FIG. 1 or from the right to the left as viewed in FIG. 1.
As the display moves in one direction, the indication informs the
user that the musical instrument is flat whereas when the display
moves in the opposite direction, the operator is informed that the
musical instrument is sharp. On the other hand, when the display is
stationary and only one of the indicator devices 14-28 repetitively
lights up, the user is apprised that the musical instrument is in
pitch. The rate at which the display sequences in either of the
opposite directions is indicative of the degree by which the
musical instrument is sharp or flat and, if desired, the
selectivity switch hereinafter described may be actuated by means
of the knob 30 either to increase or decrease the rate of display
device sequencing. Typically, the reference pitch may be adjusted
by the knob 32 to select any one of the diotonic notes of a major
scale, as for example the C major scale, so as to accommodate for
the tuning requirements of various instruments. Obviously, any
other desired arrangement may be utilized with respect to the
reference pitch.
The basic principles according to the present invention will be
seen readily from a study of FIG. 2 wherein it will be noted that
the reference generator means indicated by the reference character
42 produces a pulse train output signal at the conductor 44 which
is applied to one input terminal of the sequencing switching means
46. The microphone 40 is connected to the converter means 48 which
produces a second pulse train output at the conductor 50 which is
applied to the other input terminal of the sequencing switching
means 46. The means 46 forms part of the display means together
with the individual visual indicator devices 52, 54, 56 and 58.
Whereas eight indicator devices are illustrated in FIG. 1 and only
four are illustrated in FIG. 2, it will be appreciated that any
number of indicating devices greater than two may be utilized to
perform the functions of the present invention.
When the musical instrument under test is producing the correct
tone, the pulse train outputs at the conductors 44 and 50 are
harmonically related and one of these signals is utilized
sequentially to enable the indicators 52, 54, 56 and 58 while the
other of these pulse train outputs is utilized to energize that
single indicator 52-58 which is enabled in consonance with the prf
of such other pulse train output. Thus, when the musical instrument
is flat and a correspondingly different prf is present at its
output 50, the indicators 52-58 will be energized sequentially in
one direction whereas if the musical instrument is sharp, the
indicators will be sequentially energized in the opposite
direction.
In order to provide the requisite waveform at the output conductor
44 of the reference generator means 42 and, as well, to accommodate
for tuning to different pitches, the reference generator means is
constructed according to FIG. 3. As shown, the reference generator
means includes a highly stable crystal oscillator source 60 which
is utilized such that its stable frequency output at the conductor
62 clocks the counter 64. The counter 64 is of the type having a
plurality of output lines 66, 68, 70, 72, 74, 76 and 78 at all of
which logical ones appear when the counter has counted a full
complement of the clock pulses and with the reset cycle occupying
the next clock period. When the counter is full, logical ones
appear at all of its output conductors 66-78 and these are ANDED by
the gate 80 to produce a pulse of the pulse output train at the
conductor 44 and, as shown, the counter is reset at this time.
Thus, the counter 64 operates effectively to divide down the
frequency of the fixed and stable oscillator 60 normally to produce
an output at the conductor 44 which, in the particular instance
shown, is 1/128 the frequency of the crystal oscillator 60 (127
counts to fill the counter 64 + one clock input for reset). To
provide for pulse train outputs at the conductor 44 having
different prfs in accord with the tuning range of the device, the
coding techniques symbolically illustrated in FIG. 3 may be
employed. Thus, the terminal 82 is connected to a source of voltage
corresponding to the logical one condition and any one or a
combination of the switches 84 may be actuated to place the logical
one input on a corresponding output line 66-78 of the counter 64 so
as to cause the counter to count to any selected and desired
predetermined number at which time an output will appear at the
conductor 44 to reset the counter as described hereinabove. As will
be appreciated, the natural frequency of the oscillator 60 must
therefore be selected high enough to accommodate all of the
frequencies of interest by division with a whole number.
FIG. 4 illustrates symbolically not only the functioning of the
converter means 48 but also of the sequence switching means 46. The
converter means 48 is in the form of a conventional phase lock loop
composed of a phase detector 86, a filter 88 and a voltage
controlled oscillator 90.
As previously noted, the display means includes the sequence
switching means 46 with the indicators 52, 54, 56 and 58 and having
the two input terminals to which the conductors 44 and 50 are
connected. As illustrated symbolically in FIG. 4, the conductor 44
is connected to the clock input of decoding counter 92 which
provides successive logical one outputs at its output conductors
94, 96, 98 and 100 which are connected as individual inputs to the
AND gates 102, 104, 106 and 108. The other inputs to the AND gates
are provided in common from the conductor 50 as shown. Thus, one
input to each AND gate is enabled sequentially from the decoder 92
and the other input to each of the AND gates is effective to
energize the corresponding indicator 52, 54, 56 or 58 when
coincidence of inputs appears at the respective AND gates. Thus,
when the musical instrument is in pitch, the lower frequency input
at the conductor 50 will always coincide with one and only one of
the sequential enablings of the AND gates 102-108 and the
corresponding one and only one indicator or display device 52-58
will periodically be energized to provide the stationary display.
If the pulse output train frequency from the converter means 48 is
of either higher or lower frequency than that at the reference
conductor 44, sequential energization of the display devices 52-58
will occur, the direction of sequencing being dependent upon
whether the musical instrument is sharp or flat with respect to the
tuning device.
A preferred embodiment of the invention is illustrated in FIG. 5.
The crystal 110 of the oscillator circuit 60 is chosen to produce a
suitable frequency which for example may be 2.00024 MHz and
provides the clock input for a nine bit counter 112 whereby
basically to divide the frequency at the conductor 62 by 1024. As
noted, the counter ignores a clock pulse while reset so that the
binary number produced when all of the output lines to the counter
112 are logical ones (i.e.=1023) plus the additional clock pulse
during reset equals the maximum division which can be performed by
the counter 112. Instead of employing the switch arrangement 84 of
FIG. 3, any suitable apparatus for performing a variable ANDing
function may be utilized such as the coding disc 114 which performs
the same function. Alternatively, one may use a custom coded diode
matrix to perform a diode logic AND function. For example, Harris
Semiconductor H 1-0186 8.times.6 custom coded diode matrices may be
empolyed. The coding disc shown is simply rotated by the knob 32
correspondingly to condition the output lines of the counter 112 in
accord with the division required, the logical one input being at
the conductor 116. To provide the proper logic, the NAND gates 118,
120 and 122 are provided, all feeding the NOR gate 124 as shown. To
illustrate the coding which is necessary, with the aforesaid
frequency of the crystal 110 division by 239 generates 8369.21Hz
corresponding to the C.sub.9 ; division by 253 generates B.sub.8,
etc. and the eight diotonic tones of a C major scale may thus be
generated by proper coding at the disc 114.
The microphone 40 drives a suitable current summing amplifier 126
and the output thereof is coupled to the non-inverting amplifier
128 and also to the inverting amplifier 130. The complementary
signals appearing at the outputs 132 and 134 of these respective
amplifiers are applied respectively to the MOS transistor switches
136 and 138. As illustrated, these switches are actuated in
consonance with the output frequency of the voltage controlled
oscillator 90 to pass the complementary signals of the amplifiers
128 and 130.
The converter or processor must cope with signals ranging in
frequency from 70Hz, of widely varying mixture of am and fm
components and the criteria of minimal size, cost and automatic
operation obviate standard methods for converting the input at the
microphone 40 to the suitable digital type signals required for
operation of the device. A phase lock loop and the implementation
thereof as shown in FIG. 5 is admirably suited to provide the
proper functioning so as automatically to tune the vco 90 to the
fundamental of the input frequency or of a harmonic or subharmonic
thereof. The input signals from various sources are each a
combination of many variables and the phase lock loop is capable of
looking for and locking onto the only constant factor among them.
Because the MOS transistor switches 136 and 138 pass the wave form
unchanged to the following filter 88, and switch very rapidly, the
phase detector is highly effective for dealing with signals of high
noise or harmonic content. The vco used is voltage tunable from 60
Hz to 2300Hz to insure proper lock for inputs of 70-2100Hz and
although its frequency range does not encompass the entire musical
spectrum, notes outside this range will cause phase lock on a
harmonic or submultiple frequency without affecting operation of
the device.
Ignoring for the moment the two four bit counters 140 and 142, the
pulse train outputs at the respective conductors 44 and 50 provide
the inputs to the sequencing switching means as previously
described. As described earlier, the counter 92 generates a
sequential series of pulses at its output conductor 144. Each
output conductor of the counter 92 feeds a bistable latch shown in
FIG. 5 as accommodated in groups of four at 146 and 148. The latch
clock inputs are connected to the output pulse train at the
conductor 50 through the medium of the pulse forming circuit 150
providing at the output conductor 152 thereof pulse outputs of
approximately one microsecond duration. The latches are effective
on clock command input to store the information at their input and
to retain such information after the clock level drops. The brevity
of the pulses at 152 assures virtually instantaneous storage of the
data yet the latches retain it until the next updating which allows
a bright display from the light emitting diodes 154, 156, etc.
without resorting to short high current drive pulses.
The two counters 140 and 142 are provided for the purpose of
selectivity control and are associated with the respective switches
158 and 160 which are ganged for common actuation by the knob 30
(FIG. 1). These counters act simply as dividers to control the rate
of sequencing of the display devices for a given off-pitch
condition of the musical instrument. Thus, should the switches 158
and 160 be in the "1" position and the display devices flicker
sequentially too rapidly, their rate may be slowed by switching to
the "2" or to the "3" position. Thus, the "1" position represents
the greatest sensitivity, etc. It will be appreciated of course
that the light emitting display devices may be arranged in any
desired array such as in a circle or otherwise as may be
desired.
* * * * *