Method Of Tuning An Electronic Keyboard Instrument In Pure Scale And Apparatus Therefor

Abstract

Method and apparatus for tuning an electronic keyboard instrument in pure scale are disclosed herein. The apparatus comprises frequency modifier means such as potentiometers which are electrically associable with the normal tone generators of the instrument, said frequency modifier means being adjustable so as to influence a tone produced by said generator to have a particular frequency or pitch, and switching means for grouping said frequency modifier means for playing in a particular key. The switch means may be mechanical or electronic and a plurality of frequency modifier means are provided for each tone generator, preferably 12. The method of tuning the instrument in pure scale comprises providing the instrument with the tone generators in tune, electrically associating the frequency modifiers with the tone generators and thereafter tuning each generator in selected keys. The instrument will then play in pure scale in any particular key that is selected by the switch means. Additionally, a further set of frequency modifier means may be provided for selectively enabling the instrument to play in tempered scale.

Description

BACKGROUND OF THE INVENTION

Pure or just intonation is not a new idea per se, but has been studied throughout the years. For example, Hemholtz described an organ in the 1800's that would play in pure scale. This particular organ, however, was a manual keyboard instrument with a large number of digitals per octave. Obviously, the instrument was unwieldy due to the large number of digitals and could not be effectively played.

Pointing to the derivation of pure or just intonation, the western "diatonic" scale is a group of tones related to each other by small whole numbers, and was used many years ago for tuning keyboard instruments. As music and musical instruments became more elaborate, the diatonic scale was expanded to the "chromatic" scale. Further, as music and harmony progressed, composers began to write in different keys within the same work. For certain instruments no particular problem was encountered when pitch was adjusted slightly to insure that the tonal relationships remain correct in a new key. With conventional digitalized instruments, however, such as the pipe organ or pianoforte, the pitch of each note is fixed, and once the instrument is tuned in a particular key and played in yet another key, objectional beats result due to interaction of the harmonic of the notes being played which are not perfectly in tune.

Numerous tuning systems have been developed to minimize the out-of-tuneness referred to above. The "equally tempered" system has virtually gained universal acceptance in this regard, but does not eliminate the beats. Instead, the equal tempered scale merely minimizes "out-of-tuneness" by spreading the error across an entire octave. The equal tempered sytem is utilized today for tuning digitalized instruments with the frequency interral between each note being represented by the 12th root of 2.

While as mentioned above, an enormous number of separate keys necessary for each octave where an instrument is tuned in pure scale or by just intonation, is not practical, the current state of electronics now permits an electronic digitalized or keyboard instrument to be tuned in pure scale in every key and thereafter conveniently switched from key to key as desired. The present invention provides such a capability and is thus a substantial advance in the art. According to the present invention, out-of-tuneness in electronic digitalized instruments is virtually eliminated and the instrument is completely versatile. The present invention is neither anticipated nor suggested by the prior art, exemplary of which are U.S. Pat. Nos. 2,422,940 to Waage; 3,213,180 to Cookerly et al.; 3,235,649 to Leslie; 3,288,904 George; 3,305,620 to Young; 3,355,539 to Munch, Jr. et al.; 3,355,976 to Volodin; 3,417,189 to Kramer, Jr.; 3,427,569 to Abramson; 3,440,324 to Schrecongost et at.; 3,443,017 to Jones; 3,458,642 to Leslie; 3,484,529 to Moore; 3,490,327 to Volpe; 3,499,090 to Meyer; 3,520,982 to Malmfors; and 3,590,129 to Freeman.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method of tuning a digitalized electronic instrument in pure scale in every key.

Another object of the present invention is to provide a digitalized eleectronic instrument capable of playing in pure scale in every key and also equal temperament by a switching arrangment.

Still another object of the present invention is to provide apparatus for adapting a conventional electronic digitalized instrument to be capable of being tuned in more than one key and played in such keys.

Still further, another object of the present invention is to provide an electronic digitalized instrument capable of playing in every key, both major and minor with switching means for changing from key to key.

Generally speaking, the method according to the present invention comprises the steps of providing an electroic digitalized instrument having tunded tone generators associated with the digitals; electrically associating frequency modifier means with said tone generators, said modifier means controlling the pitch of tones produced by said generators, said frequency modifier means having key switching means associated therewith, and setting said modifier means for each generator in each key, whereby said instrument may be played in tune in more than one key.

More specifically the keyboard or digitalized instrument may be of conventional type. Preferably, the tone generators of the instrument are first tuned in a particular key, middle C, for example. Thereafter, means are electrically associated with each of the tone generators to vary the output frequency thereof and thus slightly vary the pitch of the tone produced by the generator. The frequency modifier means are then set to produce a tone of a particular pitch for each key. Switching means are further provided with the frequency modifier means so as to group the modifier means in a predetermined fashion for the particular key, whereby only the particular modifier means for the particular key are actuated to influence the tone generators. Thereafter, upon depressing a digital of the instrument, the tone produced will be determined by the influence of the modifier means on the generator for the particular digital. In this fashion, 156 notes per octave may be provided, including the equally tempered and justly intoned notes, and thus provide an instrument capable of great flexibility. Insofar as the instrument per se is concerned, the frequency modifier means and the like being electrically associated therewith have no effect on the instrument insofar as movement up and down the scale is concerned, i.e., from octave to octave. Such is conveniently handled by the standard frequency dividing networks normally utilized in the instrument or by whatever means provided.

The tone generators are those conventionally used with the electronic organ and are generally Hartley Colpitts type oscillators. The frequency modifier means are associated with the oscillators so as to control current being supplied thereto. Current to the oscillators may be added or deleted from the base of a transistor in the oscillator circuit whereby the D.C. operating characteristics of the oscillator are altered to produce a tone having a slightly varied pitch. Also, a diode may be connected in series with a capacitor across the tuning network of the oscillator with current to the diode being controlled whereby the A.C. operating characteristics of the oscillator, are altlered while the D.C. characteristics remain substantially constant. The system thus enables the tone generators to produce a sound of a particular pitch in a particular key. Depending upon the system employed for tuning, certain of the notes may be duplicates with the same note in one or more adjacent keys. As such, one frequency modifier means may be actuated for several keys, or a modifier means may be provided for each generator in each key desired. Under any circumstances, when a key is selected, a predetermined group of modifier means are actuated such that depression of a digital produces the predetermined frequency for the key in which the instrument is being played.

Generally speaking, the apparatus according to the present invention for enabling an electronic keyboard or digitalized instrument to be played in pure scale in a plurality of keys, comprises frequency modifier means, said frequency modifier means being adaptable for electrical connection to tone generators of the instrument, each tone generator having a plurality of modifier means associable therewith, and switching means assocaited with said frequency modifier means, said switching means actuating one modifier means only for each generator at any one time.

Preferably the modifier means according to the present invention comprise potentiometers which may be individually adjusted, one at a time, to control the output frequency of the tone generator with which it is associated whereby a tone of a slightly different pitch may be produced by influence of the potentiometers. In certain situations, as mentioned above, it is not necessary to use a separation potentiometer for each note in each key, though one embodimet of the present invention envisions utilizing 12 potentiometers for each key in which the instrument is to be played plus 12 for the equally tempered scale.

The particular potentiometers for the various notes in a single key are grouped by the switching means of the present invention. The switching means may comprise one of several arrangements. For example, where 12 potentiometers are utilized for each key, the switching means is set up to actuate in sets of 12 and deactivate all of the remaining potentiometers, either by passing from one matrix to another or the like. Additionally, where common potentiometers are used in more than one key, isolating diodes may be employed so as to selectively actuate or deactivate certain of the potentiometers according to the key in which the instrument is being tuned or played. As such, the potentiometers are grouped such that when contact be made between positive and negative supply in a particular area, a predetermined number of potentiometers preset to produce tones of a certain pitch are actuated and the remainder of the potentiometers are deactivated or blocked out of the circuitry.

Switch means according to the present invention generally include selector means for determining which particular group of frequency modifier means are to be employed for providing the proper pitch tones. The present invention is not restrictive in this area, though one preferred embodiment of the selector arrangement is a mechanical arrangement utilizing an appropriate number of contacts for positive and negative supply terminals, one positive and one negative contact being provided for each key in which the instrument is to be played. Electrical contact means are further provided on a nob or at individual switches so as to mechanically provide current through one set of positive and negative terminals and thus actuate predetermined modifier means. Also preferred as a selector means according to the present invention is a single octave keyboard that is associated with circuitry to electrically switch from one group of modifier means to another group so as to influence the tone generators according to the key in which the instrument is to be tuned or played. Circuitry for this particular arrangement is again not restrictive, but preferably contains integrated circuit RTL NOR gates that are connected to power switching transistors for each particular modifier means group. Moreover, a reset circuit is also incorporated among the grroups of gates and so as to actuate only the circuit corresponding to the note depressed on the one octave keyboard while deactivating the remainder of the circuits.

The various potentiometers or other frequency modifier means for each tone generator each feed into a single connector for association with the tone generator. Only the particular potentiometer of interest is, however, actuated at any one time if the output of the generator is to be changed. As such, the apparatus according to the present invention amay be conveniently maintained in a small housing with one lead per tone generator extending into and connected to the conventional electronics of the digitalized instrument. Any conventional instrument may thus be conveniently adapted to play in pure scale in all keys as well as in the equal tempered scale by the apparatus of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of an oscillator, representing a conventional tone generator being modified according to the teachings of the present invention.

FIG. 2 is a further circuit diagram of a modifieed oscillator showing another embodiment of the present invention.

FIGS. 3, 3A and 3B are circuit diagrams of potentiometer groupings and switching means according to the teachings of the present invention.

FIG. 4 is a circuit diagram of yet another frequency control means grouping according to the teachings of the present invention.

FIG. 5 is a schematic circuit diagram of an electronic switching mechansim according to the teachings of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As mentioned above, the present invention enables a digitallized electronic instrument to play in pure scale in all keys and in equally tempered scale. Having developed an apparatus suitable for realization of such, the particular pitch of each note in each key must thus be established. Pitch of a note in a particular key will vary insofar as the frequency is concerned with the particular starting point, though the interval between notes in a particular key can be established. Table I, set forth below, illustrates one set of values useable for the chromatic scale with just intonation and also the equally tempered intonation values for comparison purposes.

TABLE I ______________________________________ Just Equally Tempered ______________________________________ Unison 1/1 1.0 Sub Second 25/24 1.0595 Second 9/8 1.1225 Minor Third 6/5 1.1892 Major Third 5/4 1.2599 Fourth 4/3 1.3348 Tritone 45/32 1.4142 Fifth 3/2 1.4983 Minor Sixth 8/5 1.5874 Sixth (Major) 5/3 1.6818 Minor Seventh 16/9 1.7818 Seventh (Major) 15/8 1.8877 Octave 2/1 2.0 ______________________________________

If a definite value is assigned to one note, C, for example, values can be established for the digitals of the keyboard as illustrated under vertical column C of Table II. Furthermore, vertical column C may be expanded through the circle of fifths or fourths taking the value of the unison for the new key from its note value from the previous key, whereby the note values for each note in a new key, relaltive to the original C may be calculated. These values are set forth in Table II.

TABLE II __________________________________________________________________________ NOTE INTERVALS-JUST INTONATION __________________________________________________________________________ KEY EQUALLY D.music-flat. A.music-flat. E.music-flat. B.music-flat. F C G D A E B F.music-sharp. NOTE TEMPERED C 1.0 160 80 80 1 1 1 1 1 81 81 2025 32805 81 81 81 1 1 1 1 1 80 80 2048 32768 C.music-sharp. 1.0595 256 256 256 16 16 25 135 135 135 415 2187 2187 243 243 243 15 15 24 128 128 128 384 2048 2048 D 1.1225 800 10 10 10 10 9 9 9 9 9 729 729 729 9 9 9 9 8 8 8 8 8 640 640 D.music-sharp. 1.1892 32 32 32 32 32 6 6 6 1215 1215 1215 1215 27 27 27 27 27 5 5 5 1024 1024 1024 1024 E 1.2599 512 512 100 5 5 5 5 81 81 81 81 81 405 405 81 4 4 4 4 64 64 64 64 64 F 1.3348 320 320 4 4 4 4 4 27 27 675 10935 10935 243 243 3 3 3 3 3 20 20 512 8192 8192 F.music-sharp. 1.4142 1024 1024 64 64 25 45 45 45 45 729 729 729 729 729 45 45 18 32 32 32 32 512 512 512 G 1.4983 40 40 40 40 3 3 3 3 3 243 243 675 27 27 27 27 2 2 2 2 2 160 160 4096 G.music-sharp. 1.5874 128 128 128 128 8 8 8 405 405 405 405 6561 81 81 81 81 5 5 5 256 256 256 256 4096 A 1.6818 2048 400 5 5 5 5 27 27 27 27 27 2187 1215 243 3 3 3 3 16 16 16 16 16 1280 A.music-sharp. 1.7818 1280 16 16 16 16 16 9 9 225 3645 3645 3645 729 9 9 9 9 9 5 5 128 2048 2048 2048 B 1.8877 4096 256 256 50 15 15 15 15 243 243 243 243 2187 135 135 27 8 8 8 8 128 128 128 128 __________________________________________________________________________

Referring to Table II, the key note value is carried over from a previous key to the next key whereby a small total number of different pitches is required. This system is disadvantageous, however, in that, the sharp keys get progressively sharper and the flat keys progressively flatter. Should an instrument utilizing the intervals set forth in Table II be played by itself or with other instruments or media which can be easily shifted up or down as necessary, such as the human voice, the key note borrowing presents no particular problem. Conjunctive use of the instrument with a fretted or a fixed tune instrument such as a guitar or piano, for example, does provide a problem since it is desirable to have the average pitch remain constant through all the keys. As such, the note for each key should be tuned separately, resulting in 144 distinct pitches per octave instead of the 37 utilized in Table II. Moreover, as mentioned above, it is also desirable to provide the capability for the instrument to be tunable to the equally tempered scale, thus adding 12 additional pitches to arrive at a total of 156 pitches per octave.

A new system of deriving sharp notes has also been developed which removes the disadvantages set forth with respect to Table II. In other words, the center of tonality is maintained very constant and the sharp keys do not become sharper or the flat keys flatter with movement of the scale. According to the improved system of tuning, note intervals are set forth below in Table III.

Table III depicts note intervals derived by application of the low of combination tones. Just tuning was previously based on the diatonic scale only. Chromatic intervals, while called just were actually out of tune becuase of incorrect combination tones produced thereby. The below improved system produces correct combination in both major and minor intervals and allows a sense of melodic correctness which was not experienced by chromatic notes by provious just standards.

TABLE III ______________________________________ JUST INTONATION NOTE INTERVALS ______________________________________ C 1/1 C.music-sharp. 135/128 D 9/8 D.music-sharp. 19/16 E 5/4 F 4/3 F.music-sharp. 45/32 G 3/2 G.music-sharp. 304/192 A 5/3 A.music-sharp. 57/32 B 15/8 ______________________________________

The tuning plan for the key of C based on the above intervals is as follows: C-E-G, F-A-C, G-B-D, F.music-sharp.to D, C.music-sharp.to F.music-sharp., G.music-sharp. to C.music-sharp., D.music-sharp. to G.music-sharp., and A.music-sharp. to D.music-sharp.. When the key of C is tuned as set forth above, certain intervals appear to be out of tune in the key of C. This improved system for accidental note tuning is based on combination tones and the beats and chords in the key of C actually produce perfectly tuned combination tones. In some instances, fundamental tones react with combination tones to produce even lower combination tones. For example, for a C minor chord, C and E.music-flat. produce a lower combination tone of G and E.music-flat. and G produce an apparently out of tune E natural, but the out of tune E natural combines with the fundamental E.music-flat. and produces a low C.

Utilization of the intervals set forth in Table III, as mentioned above, maintains a constant center of tonality and further, all scales can be tuned from only 38 distinct pitches. Utilizing the intervals set forth in Table III, a system for selecting the various pitches is set forth in Table IV. In Table IV, differently from Table II, each new key is not derived from the preceding key, but rather in each key, each pitch is selected from the three or four available for each note so that the interval relationship remain constant as does the center of tonality. Differently from Table II, Table IV is indicated in sub-script. In this particular arrangement, the key note, that is the note for the key in which tuning is desired is the starting point, and like numbered sub-scripts represent like intervals.

TABLE IV ______________________________________ IMPROVED JUST INTONATION PITCH SELECTION ______________________________________ D.music-flat. A.music-flat. E.music-flat. B.music-flat. F C G D A E B F.music-sharp. 3 3 3 2 1 C.sub.1 1 2 2 2 1 1 1 1 2 2 1 C.sub.1 .music-sharp. 1 1 1 1 3 3 3 3 3 3 2 D.sub.1 1 1 1 4 4 4 1 1 1 1 1 D.sub.1 .music-sharp. 1 2 2 2 2 2 3 3 2 2 1 E.sub.1 1 4 4 4 4 4 2 2 3 3 1 F.sub.1 3 3 3 3 1 1 1 2 2 2 1 F.sub.1 .music-sharp. 1 1 1 3 3 3 2 2 2 2 1 G.sub.1 1 1 3 3 3 1 1 1 1 4 1 G.sub.1 .music-sharp. 2 2 2 2 2 3 4 2 2 2 1 A.sub.1 3 3 3 3 3 3 3 1 1 1 2 A.sub.1 .music-sharp. 1 1 1 1 2 2 2 2 2 3 1 B.sub.1 1 1 4 4 4 4 ______________________________________

Having thus set forth two preferred arrangements for tuning the digitalized electronic instrument in pure scale, the apparatus and method of the present invention will now be described in detail, making reference to the Figures.

FIG. 1 illustrates a typical transistor oscillator in the Hartley configuration which is exemplary of tone generators for digitalized electronic instruments. In FIG. 1, however, the oscillator has been modified to vary the frequency output therefrom according to a preferred arrangement of the present invention. The oscillator generally indicated as 10 thus includes a transistor 11 with the base and emitter having resistors R.sub.c, and R.sub.e in series therewith and the base having resistors R.sub.b and R.sub.e in series therewith. The tuning network of the oscillator contains two capacitors C.sub.c and C.sub.rc in addition to a tunable coil L.sub.rc. A connector 12 leads into the base of transistor 11 and has a resistor R.sub.t therein. Connector 12 is further associated at an opposite end thereof with a number of tuning controls, illustrated by the controls, C.sub.1, C.sub.2 and C.sub.3. As will be described in detail hereinafter, depending upon actuation of the switching network, C.sub.1, C.sub.2 or C.sub.3, etc. will be actuated in a particular key so as to provide input to oscillator 10 through connector 12 and resistor R.sub.t. Depending upon the input, the frequency output of oscillator 10 will be varied slightly so as to slightly vary the pitch of a note being produced by depression of the digital C in the particular key being played. Insofar as the present invention is concerned, the electrical means for converting oscillation to the tonal output is not within the purview of the present invention. Such is felt to be well within the purview of one skilled in the art as being conventional apparatus on a commercial digitalized electronic instrument and thus is not described herein. Suffice it to say that once a particular key has been selected and the digital C is depressed along the keyboard of the instrument, the particular control of the selected key is actuated while the remainder of the controls are deactivated whereby the selected control determines the particular pitch of the output from oscillator 10.

In the particular arrangement as shown in FIG. 1, the current from controls C.sub.1, C.sub.2 or C.sub.3 is influencing the current at the base of transistor 11 to alter the D.C. operating characteristics of the oscillator. According to the embodiments shown in FIG. 1, the particular tuning control is selected and the remainder of the tuning controls omitted through the use of isolating diodes for those tuning controls other than C.sub.1. The utilization of this particular scheme of operation will be further described herein.

Making reference to FIG. 2, a further Hartley oscillator generally indicated as 20 is illustrated as being adapted to vary the frequency output of the oscillator so as to change the pitch of a tone generated thereby in a digitalized electronic instrument. Oscillator 20 generally differs from the oscillator illustrated in FIG. 1, in that, a capacitor C.sub.t and a diode D.sub.c are connected in series and are parallel to the tuning network. A connector 212 having a plurality of resistors therein is associated with diode D.sub.c at one end and with the key switching network at an opposite end. Depending upon the tuning control actuated, current passes through connector 212 and changes the resistance of diode D.sub.c. A change in the resistance of diode D.sub.c causes a proportional effect in capacitor C.sub.t which alters the A.C. characteristics of oscillator 20, while the D.C. characteristics of oscillator 20 remain substantially constant. A lesser amount of current passing through connector 212 operates to create a greater frequency output from oscillator 20 thus slightly raising the pitch of a tone generated thereby.

One preferred arrangement will now be described for actuating the desired controls to influence tone generators of the digitalized instrument and thus produce tones of particular pitches in particular keys. In essence, FIGS. 3, 3A and 3B represent three separate control matrices with FIG. 3 representing the flat key diode matrix, FIG. 3A the middle C diode matrix and FIG. 3B the sharp key diode matrix. The three matrices in operation would be positioned side by side or otherwise with suitable switching means associated therewith. The switch means would make contact with certain of the terminals thus actuating certain of the modifier means while disassociating the remaining modifier means (tuning controls), whereby the tone generators will be influenced by the operational modifier means only.

As will be further pointed out hereinafter, the switching means for actuating and/or deactivating the tuning controls associated with the various keys can be any suitable switching arrangement that will make contact at the appropriate points. For example, a rotatable selector may be provided, rotation of which moves a pair of electrical contacts across the span of the matrices, the contacts on the selector switch making contact with the positive and negative supply terminals of the matrices at the particular points indicated on the Figures. Referring back to FIGS. 1 and 2, it is pointed out that the controls C.sub.1, C.sub. and C.sub.3 are connected to a single lead into the oscillator. Such would likewise be the case with respect to FIGS. 3, 3A and 3B, in that, all of the C controls would be connected into one lead into the C tone generator. Such connection has not been shown on FIGS. 3, 3A and 3B so as to simplify the diagrams. In each case, the lead would be associated with the center tap of the potentiometers.

In FIGS. 3, 3A and 3B, note that middle C is not connected to either of the other matrices. As such, once the instrument is tuned in pure scale in the scale of C, each note will produce a tone in a pitch of C unless influenced by a further control. Note also, for example, that in the key of F, only A and D are influenced. In this situation, all of the notes of the octave would be in the same pitch as in the scale of C except for A and D. In both of these situations, controls A.sub.2 and D.sub.2 respectively would influence the oscillator for the A and D tone generators so as to produce a tone of slightly different pitch. Similarly, with the other keys, only certain tone generators are affected and those not listed would produce tones according to the pitch in the scale of C.

According to FIGS 3, 3A and 3B, each tuning control is preferably a potentiometer bracketed by isolating diodes so as to preclude inadvertent actuation of same. The isolating diodes possess a greater reverse breakdown than the supply voltages. Moreover, while as shown in FIGS. 3, 3A and 3B various groups are produced again by isolating diodes, it is also possible to have further isolating diodes connected with each control. The grouping arrangement, however, reduces substantially the number of diodes required and is thus most preferred. Likewise, other possible diode variations are conceivable, though not specifically illustrated herein. Still further, as mentioned above, each key may be provided with 12 separate frequency modifier means, one for each note of the scale. With such an arrangement, once the instrument is being played or tuned in a particular key, only the controls in that key are actuated and all of the remaining controls receive no power. Each of the tone generators for the various digitals is thus influenced by a separate potentiometer in each key. While not particularly illustrated for all keys, each key circuit would take the form as shown in FIG. 3A for middle C. In other words, instead of providing one matrix having 12 controls for middle C, each key would have 12 controls associated therewith, thus providing a system with 144 controls for just intonation or 156 controls for just intonation and equally tempered scale. Still making reference to FIG. 3, assume that the instrument is to be played in the key of B flat (B.sup..music-flat.). A positive voltage from the positive supply passes through the diode 31 and actuates controls B.sub.3, G.sub.4 .music-sharp. and C.sub.2. Simultaneously, diodes 32, 33 and 34 will be reversed biased thus deactivating G.sub.2, D.sub.3, F.sub.2 .music-sharp., E.sub.2 and C.sub.2 .music-sharp. from influencing the tone generators to which they are connected. Hence, other than B.sub.3, G.sub.4 .music-sharp. and C.sub.2, middle C tuning of the other notes would prevail. Likewise, when switching to another key, certain of the controls will be actuated while others will be deactivated according to the particular arrangement for achieving just intonation of the instrument.

FIG. 4 illustrates another arrangement for the frequency modifiers for sharp keys according to the present invention. The arrangement of FIG. 4 does not duplicate middle C and the flat keys since both would be designed according to the same scheme. The arrangement of FIG. 4 performs in a manner very similar to FIGS. 3, 3A and 3B, though since duplicates of modifier means are not shared as often as in the groups of the FIG. 3 arrangement, a substantially larger number of potentiometers and diodes are necessary.

FIG. 5 illustrates a particular electronic switching mechanism for shifting from key to key and thus actuate the desired frequency modifier or control means for the particular key selected. A key switch 50 is electrically associated with integrated circuitry containing RTL NOR gates (resistor, transistor, logic) gates 51, which, in turn, is connected to a power switching transistor circuit generally indicated as 60. Switching transistor circuit 60 is electrically associated with the positive and negative contacts along the diode matrices as indicated by the contacts for the various keys. In actuality, one RTL NOR circuit and power switching transistor circuit is provided for each key in the system. Furthermore, a reset circuit generally indicated as 70 is also provided and is electrically associated as shown in each of the RTL NOR circuits. The reset circuit deactivates all of the RTL NOR circuits except for the one for which the particular key 50 is depressed. For example, one circuit for each note of the scale and one for equal tempered tuning, when the equal tempered key 50 is depressed, the RTL NOR circuit for equal tempered scale is actuated by providing a positive voltage at point 52 which, in turn, actuates power switching transistor 60 to actuate positive and negative supply to the equal tempered switching network. Simulateously, the reset circuit 70 removes voltage from like points 52 of all other RTL NOR circuits except for the one for equal temperament. All remaining power switching transistor networks of the system are then deactivated until another key is depressed.

Utilizing the electronic switching arrangement of FIG. 5, a single octave keyboard may be provided, with each note representing one key. Depression of the particular digital on the keyboard would then actuate the frequency modifier means for the key. As further illustrated in FIG. 5, an indicating lamp 62 is provided which will illuminate when the power switching network is actuated and thus indicate the particular key in which the instrument is set to be played.

A preferred tuning arrangement includes tuning an instrument, such as an organ, having 12 tone generators in just intonation in the key of C. Thereafter, the frequency modifying apparatus of the present invention is connected to the organ such that one lead is electrically associated with each tone generator. Thereafter, the organ is returned in every desired key, for example, all of the keys of the scale, Tuning is accomplished by setting the selector switch to the desired key for tuning which incorporates preselected frequency modifier means as hereinbefore mentioned while leaving other of the tone generators as tuned in the key of C. The particular tone generators having controls associated therewith are then tuned by simultaneously depressing certain digitals and listening to the beat frequencies and combination tones produced. In the event a beat is produced, the frequency control means is adjusted by movement of the center tap of the potentiometer until the beat disappears. At that point, the particular tone generator is in tune in the particular key. This sequence is repeated for every key in which it is desirable to tune the instrument. Thereafter, the instrument may be indiscriminately played in any desired key merely by movement of the selector switch to the particular desired key. At that point the switching network automatically actuates the prescribed control means such that when a digital is depressed the tone generator for the particular digit will produce tone of a particular pitch, either the pitch for just intonation in the key of C or for a modified pitch.

As also mentioned hereinbefore, once the tone generators of the digitalized electronic instrument are tuned in pure scale utilizing the techniques according to the present invention, movement up and down the keyboard is handled by conventional electronics in the instrument.

Having described the present invention in detail, it is obvious that one skilled in the art will be able to make variations and modifications thereto without departing from the scope of the invention. Accordingly, the scope of the present invention should be determined only by the claims appended hereto.

Claims

What is claimed is:

1. Apparatus for enabling an electronic keyboard instrument to play in various keys comprising:

a. a plurality of tone generators, said tone generators being electrically associated with digits across said keyboard, each generator being associated with only one digit per octave; and

b. a plurality of frequency modifier means associated with each tone generator, each said modifier means being adjustable according to predetermined intervals to cause the generator to emit a sound of a particular pitch, said modifier means being grouped according to a particular musical scale, and electronic switching means associated with said modifier means to activate certain modifier means only in each key, said switching means comprising a plurality of individual actuator means, each actuator means having an integrated circuit coupled thereto, said integrated circuits containing RTL NOR gates and power switching transistors coupled thereto, each said power switching transistor being further coupled to one group of modifier means whereby actuation of one of said integrated circuits actuates only the group of modifier means to which the power switching transistor for said acutated integrated circuit is coupled.

2. Apparatus as defined in claim 1 wherein 12 integrated circuits are present and wherein a reset circuit is electrically coupled to said power switching transistor of said integrated circuit, said reset circuit causing removal of voltage from all power switching transistors other than the one coupled to a selected actuator means, thereby deactivating all of said remaining power switching transistors.

3. Apparatus for enabling an electronic keyboard instrument to play in various keys comprising:

a. a plurality of tone generators, said tone generators being electrically coupled with digits across said keyboard, each generator being coupled with only one digit per octave; and

b. a plurality of potentiometer frequency modifier means electrically coupled to each tone generator, said modifier means being adjusted according to the following intervals in a key of C of

with the remaining keys being grouped and predetermined using sub-script instead of fractional intervals, maintaining a constant center of tonality and interval relationship and using as a starting point a particular note for the key in which tuning is desired, as provided in Table IV, said potentiometer frequency modifier means having isolating diodes positioned on opposite sides thereof and coupling said potentiometers and a power supply, whereby in a selected key the grouping of potentiometers for said key influences the tone generators for each digit to emit a justly intuned sound.

4. Apparatus as defined in claim 3 wherein each tone generator has 12 potentiometers coupled thereto.

5. Apparatus for enabling an electronic keyboard instrument to play in various keys comprising:

a. a plurality of tone generators, said tone generators being electrically coupled with only one digit per octave;

b. a plurality of potentiometer frequency modifier means electrically coupled to each tone generator, said potentiometers being adjustable according to predetermined intervals, said potentiometers further being grouped according to a particular musical scale and having isolating diodes located on opposite sides thereof and said diodes being connectable to a source of power supply; and

c. switching means to connect one group of said potentiometers only to said source of power supply whereby said connected potentiometers influence the tone generators to which they are coupled, while isolating diodes preclude interference from the other of said potentiometers.

6. Apparatus as defined in claim 5 wherein said potentiometers are adjusted according to the intervals set forth in Table II.