US3509454A - Apparatus for tuning musical instruments - Google Patents

Description

April 2s, 1970 .0; IGOYS'SEL 3,509,454

APPARATUS FOR TUNING MUSICAL INSTRUMENTS Filed Oct. 19, 1965 4 Sheets-Sheet 1 VARIABLE FREQ UENCY GENE 2 TRANSDUCER 7 Fm FREQUENCY DIVIDER 2 SQUARING A. 4 Z AMPLIFIER A FREQUENCY U COMPARISON A cmcun' 2 B O f v fm 5 MAGNETIC PICK UP gg gggMAcNE l IL PHASE SENSITIVE INDICATOR AMPLIFIER] Fig. la

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APPARATUS FOR TUNING MUSICAL INSTRUMENTS Filed Oct. 19, 1965 4 Sheets-Sheet z A B Q f k f/2 f/4 I49 U UV 6 Um Uc INVENTOR. DIETER GOSSEL BY w l s i" AGEN April 28, 1970 D. GOSSEL 3,

APPARATUS'FOR TUNING MUSICAL INSTRUMENTS Filed Oct. 19. 1965 4 Sheets-Sheet 5 Fig.4a

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v APPARATUS FOR TUNING MUSICAL INSTRUMENTS Filed Oct. 19, 1965 4 Sheets-Sheet 4 DIETER GOSSEL BY M AGENT United States Patent Int. Cl. Gtin 23/14 US. Cl. 32479 4 Claims ABSTRACT OF THE DISCLOSURE Apparatus for tuning musical instruments which uses a digital divider to produce two frequencies which differ by one musical half tone. The resultant frequencies are compared in a phase sensitive comparator which optically indicates the frequency differences.

Musical instruments having a series of selectable tones are known, for example key instruments.

Since for reasons of structure and technique of playing such instruments can have only a limited series of tones which may be played it is necessary to have a program according to which individual tones may be selected. Several such selection programs are known. They are exemplified in the various musical systems or tunings, substantially the pythagoreic tuning, the natural tuning, the mean-tone temperament and the equal temperament.

The equal-tempered musical system is used today in substantially any key instrument. The circle of quints is closed by relatively equal tones, tempered quints. The tempering consists in the uniform distribution of the ratio (531,44l:524,288) indicated as the pythagoreic comma, which is the residue of seven pure octaves, over the twelve quints. That is to say, the equal-tempered quint is diminished by only one twelfth pythagoreic comma (-l001) relative to the pure quint. The advantage of the closure of the circle of quints (unlimited continuous possibility of modulation) is obtained at the expense of comparatively shrill major thirds and muted minor thirds.

The tuning of the oscillators (cords, pipes, tongues, electronic generators) of instruments with fixed tones is usually effected in quint intervals with equal temperament. It is the art of the tuning operator to find the very temperament at which the circle of quints closes after twelve steps. In principle not only the quint but also the fourth, the major seventh and the minor second (half tone) are suitable for tuning. When tuning is effected in half tones the adjustment to the initial octave, which is otherwise always necessary, could even be dispensed with. However, tempering of a dissonant is almost impossible by ear so that the consonant intervals quint and fourth are preferred.

Even in this case correct tuning by ear requires concentration, time and an ear trained for music. It is carried out by a number of experts which nowadays decreases more and more.

The present invention relates to an oscillator for a musical instrument and is characterized in that audible frequencies constituting intervals used in music may be derived from a high-frequency oscillation using switchable digital frequency dividers having predetermined integral ratios of division.

With the new oscillator for a musical instrument it is possible, for example, to construct a tuning device which produces accurate, equal temperament within a very short time. Tuning to the correct pitch is effected by optical means, for example using an indicating instrument, and does not require any training of the tuning operators ear for music. The operation is so simple that such an electronic tuning device may be delivered 'with certain key instruments, as anauxiliary part leaving the occasional tuning to the user. An important application of a tuning device including the new oscillator is with church organs which often require retuning because of the seasonal fluctuations in temperature. Especially with comparatively large-size mechanisms this has hitherto been laborious and time-consuming because of the many different registers and pipes.

However, with the new oscillator for musical instruments it is also possible to manufacture uniphonic or polyphonic instruments. The structure is similar to that of the tuning device for either type. The most essential difference is that the uniphonic version includes a switchable frequency divider which provides twelve different quotients, whereas the polyphonic version includes at most twelve dividers each of which provides at least one quotient.

All instruments have in common that they cannot fundamentally get out of tune since all tones are derived from a common master frequency f by numerical division, and that all tones may be transposed at will by merely varying f The kind of the tuning desired and, as the case may be, the accuracy with which individual intervals must be obtained are a measure for the choice of the dividers.

In order that the invention may be readily carried into effect it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 shows an arrangement for the tuning device;

FIG. 1a shows an arrangement for sustaining oscillations in a string;

FIG. 2 shows a switching possibility for octave dividers;

FIG. 3 shows one of the possible circuits for the frequency range;

FIGS. 4a and 4b show diagrams;

FIG. 5 shows an arrangement for uniphonic musical instrument; and

FIG. 6 shows an arrangement for a polyphonic musical instrument.

As is well-known in the digital technique, a certain frequency f may be divided by any arbitrary integer z. If 2 is comparatively large is usually counted in a counter which after the preselected number 1, provides a reset pulse, which resets the counter so that it may again count to z. The recurrence frequency of the reset pulses is f /z. It is readily possible for z to be chosen so that the associated frequencies constitute intervals serviceable in music.

If, for example, 2 :2 and 2 :1 we have and a pure quint results. All the remaining intervals may be obtained in a similar manner. An important advantage of this digital method is the independence of the intervals from f The absolute position is changed by varying i which may advantageously be done for transposition. With these means it would be possible to carry out musicaesthetic investigations and is compared differentlytempered and pure chords relative to one another and as a function of the absolute pitch in a simple and rapid manner.

With equal temperament the intervals are given by the law With positive 11 consisting of whole numbers except v=l2 (octave)-irrational numbers are concerned which cannot be composed accurately by producing digital intervals. However, it has been found that the equal-tempered half tone interval is approximated by the quotient 196/185 withan error of only 5X10- This fact and the possibility for intervals produced by frequency division to be shifted arbitrarily in absolute height make possible the construction of a tuning device as shown diagrammatically in FIG. 1..-

The output signal from a frequency generator 1 having the frequency t which is continuously variable between, for example, 40 kc./s. and 90 kc./s. in a range a little larger than an octave, is applied to a divider stage 2 which can selectively divide by z =196 or z =l85. Thus,.two frequencies f =f 196 and f =f /185 are available one after the other at the output A of the divider 2. and, if f is constant, these frequencies are spaced apart almost exactly an equal-tempered half tone.

The frequency of, for example, the tone to be tuned is compared via a transducer 3 matched to the relevant apparatus, after amplification and pulsation in squaring amplifier 4 as f with f or f as f in a direct-reading frequency-comparison circuit 5.

The indication 6 is phase-sensitive and preferably takes place by optical means. Upon tuning one observes a beating which slows down more and more (fluctuating deflection of an instrument, slowly flickering glowlamp, etc.) and which disappears with accurate equality of frequencies (constant deflection, constant brightness).

The tuning process is as follows:

(a) Adjust the frequency generator 1 to the internal, possibly quartz-controlled standard frequency of 81.4000 kc./s. In position z ==185, f =440 c/.s. and with this frequency the tone a of the relevant instrument may be tuned. As a matter of fact, a may lie at any other desired height, for example 435 c./s.

(b) Change over to z =196. The comparison frequency has now decreased by a half tone and with this frequency a flat is' tuned.

(c) Switch back to z =185 and decrease f until corresponds to 'the pretuned a fiat.

(d) Change over to z =196 and tune the tone g.

(e) Switch back to z =185 and decrease f until f corresponds to the pretuned g.

(f) Change over to z =l96 and tune the tone g flat etc.

All necessary intervals are found and lastly the octave reached again by shifting a half tone downwards or upwards twelve times. The octave is found with an accuracy of approximately 6 1O making allowance for the cumulative error of a half-tone step of 5 X For comparison let it be assumed that the smallest deviation from the prime which is still distinguished by the ear in the most sensitive pitch range of 1 kc./s. lies at 4 1O- and. hence two orders of magnitude higher.

If there is need for tuning, in addition to the twelve notes in the central position, the parallel octaves in the bass or discant it is possible in a simple manner, as shown in FIG. 2, to switch a chain of octive dividers 7 respectively, into the comparison branch at A (bass) and into the measuring branch at B (discant). The octave dividers are simple,bistable multivibrators which bring about a frequency division by two.

One of the possible frequency-comparison circuits is shown in FIG. 3; its operation is illustrated in FIGS 4a and 4b.

It is assumed that the measured voltage and the reference voltage U and U respectively can assume only two values, namely zero value and the negative maximum value. Further the width of pulse must be constant.

The arrangement is built up as a NOR circuit with a transistor 8; the presence of one of the two input voltages suffices for completely switching-on transistor 8. If both input voltages are zero the transistor 8 is cut off.

If the. measuring and comparison frequencies are different (FIG. 4a) a series of pulses U having periodically varying widths appear at the collector of transistor 8. Accordingly an instrument 9 indicates a direct current likewise-of variable mean value U If f and f, are equal U has a constant width of pulse which depends upon the accidental phase position. Consequently the instrument 9 remains at rest.

By the optical method described it'is also well possible to indicate very slow interference tones of, for example, 0.01 c./s. which cannot be heard by the ear.

The transducers employed depend upon the kind of instrument. A microphone is advantageously used with organs. For the piano a special magnetic pick-up 30, as shown in FIG. la is suggested which is attached by magnets 33 to the normally ferromagnetic strings adjacent the string to be tuned, thereby damping these adjacent strings. The pick-up also includes a small transistor amplifier 31 which completes a feedback circuit 32 by which the cord to be tuned is set into continuous oscillation.

Continuous oscillating of the measuring object is necessary to permit accurate comparison of frequencies.

The tuning of an electronic musical instrument is easiest since in this case an electro-acoustic transducer is not required, alternating voltages of the required frequencies already being available in the instrument.

The described digital tuning device is permitted to obtain a faultless equal tempered tuning of an electronic musical instrument within a few minutes, starting from an arbitrary out of tune condition.

FIGS. 5 and 6 show diagrammatically the structure of musical instruments for one voice and a multiple of voices respectively. An oscillatory source 10 feeds the oscillation frequency f into a divider 11 from which the tones, for example, in the sequence of the tones if an octave, are obtained by means of keys Z1 to Z12 connected to the individual dividers. The individual notes in the desired octave may be applied to a reproducing device 12 by means of octave dividers OT and switches S to S.

In FIG. 6, for musical instruments for multiple voices a series of octave dividers 0T 0T etc. is connected to each of dividers 1:2 l:Z etc. which are connected in parallel, whilst groups of switches S to S S to 8' etc. are provided so that arbitrary combinations of tones may be applied to the reproducing device 12.

What is claimed is:

1. Music apparatus, comprising a variable frequency oscillator, a first digital frequency divider, a second digital frequency divider, said first and said second digital dividers having division ratio approximately equal to 196/ 185, means for connecting aid first and said second digital dividers to said oscillator, means for detecting a frequency difference between the output of each of said dividers and different tones of a musical instrument.

2. Apparatus as claimed in claim 1 further including octave divider means having a division ratio of /2, and means for selectively connecting said octave divider means to each of said digital dividers.

3. Apparatus as claimed in claim 1, further comprising indicator means connected to said detecting means for optically displaying the difference between the tones of said instrument and the output of said dividers, and wherein said detecting means comprises transducer means for converting the tones of said musical instrument into electrical oscillations.

4. Apparatus as claimed in claim 3, wherein said detecting means further comprises positive feedback means connected intermediate said transducer means and said 5 6 musical instrument for providing a reinforcing oscillating 2,153,800 4/ 1939 Holmes. magnetic field within said instrument, thereby to sustain 2,521,789 9/1950 Grosdolf 331-18 oscillations. 2,892,944 6/ 1959 Wu.

References Cited HERMAN KARL SAALBACH, Primary Examiner UNITED STATES PATENTS 5 P. L. GENSLER, Assistant Examiner 2,403,090 7/1946 Larsen 841.23 X US. Cl. X.R. 2,566,085 8/1951 Green 328-30 84--1.01; 328134 3,236,931 2/1966 Freeman 32848 X

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