Modular, Expandable Digital Organ System

Electronic organs have been known for many years. Early electronic organs used various electro-mechanical devices for generating electrical oscillations corresponding to musical tones. Various types of electronic oscillators have been used to provide such oscillations. Some organs have used an independent oscillator for each tone. This is an expensive construction, and for cost saving reasons, it has been common practice to provide twelve oscillators to provide the semitones of the top octave, and to use divide-by-two circuits to provide the tones in lower octaves. More recently, it has become well-known to use a single radio frequency oscillator with divider circuits of different divider ratios to produce the top octave of tones. This system is sometimes known as a top octave synthesizer (TOS). Strings of divide-by-two circuits have been used to provide the notes in lower octaves of the organ. However, organs using these techniques have had only limited capability for expansion and were modular through historical evolution of sub-system elements rather than overall system design.

With the advent of reliable large scale integrated circuits (LSI) chips efforts have been made to construct electronic organs utilizing digital circuits. It is relatively easy to construct LSI chips that utilize digital circuits whereas it is relatively difficult to utilize analog circuits in such LSI chips. A need therefore remains for an organ system which is essentially completely digital in nature to take advantage of the full potential of integrated circuit technology.

It is an object of this invention to provide an electronic organ in which essentially all of the organ functions are obtained by carrying out logical and arithmetic operation on digital square and rectangular wave forms.

It is an object of the present invention to provide an electronic organ in which a very high percentage of the functional parts is provided on digital integrated circuit chips.

A further object of the present invention is to provide a modular electronic organ having a plurality of LSI chips therein, which chips can be duplicated or substituted to provide a very basic and inexpensive electronic organ through a very complex and expensive electronic organ.

In carrying out the aforesaid objects and other objects and advantages in accordance with the present invention, an electronic organ or other electronic keyboard musical instrument is constructed of a plurality of large scale integrated circuit chips with different families of chips wherein certain thereof can be used in conjunction with one another, or substituted for one another, thereby providing a large degree of flexibility of construction of an electronic organ in a modular system. Letter designations are used hereinafter for various chips for best reference and understanding thereof. Thus, a rhythm chip is designated as an A-1 chip that has rhythm functions thereon. A chording chip is designated as an A-2 chip, while different types of B chips are used as keyer chips depending on the nature of the keying and voice functions desired. The chips interact with one another, and are not simply compartmentalized.

The A-1 chip provides both rhythm and control of multiplexing. Among the rhythm functions are frequencies for rhythm voices and also a noise source. Multiple A-1 chips may be used to provide more complex rhythm patterns and to provide more rhythm voices.

The A-2 chip provides both chord and bass frequency generation. The chords may be played in an automatic single finger mode on a twelve note section of the keyboard or manually on an eighteen note section of the keyboard.

The chord notes may be played in a latched or an unlatched mode. Each audio output of the A-2 chip is under an independent envelope that has control of all attack and decay characteristics. The A-2 chip receives trigger information from the A-1 chip for the chord and bass audio outputs so that these may be timed with the rhythm of the A-1 chip. The A-2 chip works in conjunction also with the B chips so that all may share the same keyboard without interfering with one another.

The B chips, which are keyer chips, are primarily of two major types. In the first type, the frequency generators on the chip may be assigned to any place on the keyboard. As is common in organ constructions, a number of keys on the keyboard may be 37, 44 or 61. The second class of B chip has generators thereon which can only be assigned to one octave span of a keyboard. The number of generators is limited to a predetermined number per keyboard or manual, and are thus non-redundant. Various frequency outputs are independent of one another under two types of envelope, namely sustain or percussion. Each B chip provides various groups of audio outputs, each with its own characteristic spectral content or waveform duty cycle at various footages depending on the chip. Multiple use of B chips in any combination provides on a single manual multiple pitches, envelopes and envelope characteristics per key. All chips in the system are operated from a single data clock so that operation of any chip at any time is synchronized with the operation of other chips.

Partitioning of the circuit functions among a set of chips in accordance with this invention provides increased flexibility in the types of organs that can be assembled from the same basic chip types. As will be seen in further detail, essentially all of the organ functions are achieved in this invention by carrying out various logical and arithmetic operation on digital pulse trains. In this manner, for example, different tones are produced, different voices are provided, percussion sounds are produced, chords are recognized and synthesized, undesirable locking of oscillators is avoided, controllable attack and decay is provided, and the like. For these reasons, an organ in accordance with this invention is a true digital organ whereas typical prior art organs utilizing some digital circuits are essentially analog organs with digital appendages.

FIG. 1 comprises a schematic wiring diagram of the overall system of an entire electronic organ constructed in accordance with the principles of the present invention;

FIG. 2 comprises a block diagram with details of wiring for switching back and forth between two A-1 chips;

FIG. 3 is a schematic diagram showing certain functions of a B-2 chip and the interconnection of two B-2 chips;

FIG. 4 is a block diagram showing the connection of a plurality of B-4 chips; and

FIG. 5 is a block diagram showing the interconnection of a large number of B chips of three different varieties.

Attention now should be directed to FIG. 1 wherein the keyboard of an electronic organ or other electronic musical instrument is identified generally at 10. The keyboard includes both key switches and function switches, the latter generally being stop tablet controlled for various organ voices and features of the organ. The keyboard is interconnected at 12 with a multiplexing unit 14 which is controlled through seven control lines 16 by an A-1 chip 18 having rhythms and multiplex control. A full disclosure of the A-1 chip may be found in the copending application of Harold O. Schwartz and Dennis E. Kidd filed June 20, 1978 under Ser. No. 917,311. The A-1 chip 18 which is controlled by a tempo clock 20 is disclosed functionally. A tempo sync line 22 may interconnect the A-1 chip 18 with a second, optional A-1 chip 18a. A break pulse line 24 also interconnects the A-1 chip 18 with the optional second A-1 chip 18a. In order to avoid duplication of explanation, connections to and from the second optional A-1 chip are identified with the same numerals as those used for the first chip 18, but with the addition of the suffix a.

It has been mentioned heretofore that the A-1 chip is under the control of the tempo clock input at 20, and this is for the rhythm timing. A data clock is also connected to the A-1 chip 18 at 26, to insure proper synchronization of data to all the chips in the system. In addition to the connections to the A-1 chip 18 previously discussed, there is a plural output 28 to the rhythm voicing unit 30, which has an output at 32. No matter how many A-1 chips may be used in the system, the outputs of all of them are connected to the same rhythm voicing unit. The multiplexing control lines 16a from an optional A-1 chip 18a may be used to control a different multiplexing unit for a different keyboard (such as is typically provided on a more complex organ) than the control lines 16 from the first mentioned A-1 chip 18.

The multiplexed serial data produced by the multiplexing unit 14 is provided on an output line 34 to a junction point 36. The serial data from the junction point 36 is transmitted by way of a connector 38 back to the A-1 chip 18 (and any second or more optional A-1 chips as 18a). A second connection 40 from the junction 36 carries the serial multiplex data to an A-2 chip 42. Again, functions of this chip are set forth in the present disclosure, while circuit details of this chip are to be found in the copending applications of William R. Hoskinson and Harold O. Schwartz, filed June 20, 1978 under Ser. No. 917,312 and the copending application of William R. Hoskinson and William V. Machanian filed June 20, 1978 under Ser. No. 917,305. The data clock line 26 is connected at 44 to the A-2 chip to insure proper synchronous operation with all other chips in the system. The A-1 chip 18 has an output leading at 46 to an input of the A-2 chip 42. In addition, there is a system strobe line 48 connected through all of the chips including the A-2 chip 42 at 50. There is a redundant data counter in each chip disclosed herein. If any one counter goes to zero it pulls down the system strobe and all counters are reset to zero. This is a wire OR function which is normally held high.

The A-2 chip 42 has two outputs. One output at 52 carries the chording information. Another output 54 carries the multiplexed serial data, and may be considered as an extension of line 40 except that some data present on line 40 may not appear on line 54. The serial data line 54 leads to a first keyer or B-chip 56 which has a data clock input at 58 and a system strobe input at 60. The serial data line 54 has a junction and continues at 62 for connection to other B chips. Some details of connection are shown in subsequent figures, and for the present it is only noted that there are additional B chips 56a, 56b and 56c, all connected to the system strobe, data clock and serial data the same as the first B chip 56. Some details of the B chip will be set forth hereinafter, and others are to be found in copending applications hereinafter to be identified.

Each B chip has an output 64, and these outputs along with the outputs 52 of the A-2 chip 42 and the output 32 of the rhythm voicing unit 30 are connected to an input 66 to filters 68 and then on to an amplifier 70 feeding a loudspeaker 72 or other suitable electro-acoustic transducer.

The manner in which one or another of the A-1 chips is operative will be understood with regard to the D flip-flop 74 in FIG. 2. The flip-flop has its D input tied to a positive voltage source B+ on a line 76. The break line 24 carrying the break pulse is applied to the C input of the flip-flop 74. The output of the break pulse of the second or optional A-1 chip is carried on the break line 24A to the reset input of the flip-flop 74. The Q output on a line 78 leads to a chip enable input 25a of the second A-1 chip. Similarly, the Q is connected on a line 80 to the chip enable pin or connection of the first A-1 chip. When the flip-flop of FIG. 2 is used with two A-1 chips including the optional one in FIG. 1, some point or points in a rhythm pattern will produce a break pulse on the appropriate break line to cause the flip-flop 74 to change state to enable the other A-1 chip. Thus, a coordinated section of rhythms may alternate, or sequence in the case where flip-flop 74 is only one stage of a multiple stage shift register controlling several A-1 chips.

It is contemplated that instead of the flip-flop of FIG. 2, an X bit counter could be used to alternate the A-1 chips on other than a strict flip-flop basis. This would also make it possible to utilize more than two A-1 chips. By use of two or more A-1 chips connected in parallel, additional rhythm patterns can be established. Series connection of A-1 chips allows a larger word count for a given rhythm. The rhythm program could be operated on 24 or 48 counts with the first half in one chip and the other half in the second chip. Two 48 count patterns could be provided to give a total of 96, which would allow the use of three 32 count rhythm patterns which is sometimes desirable.

Before turning to a further discussion of the relationship of the B chips to one another, attention should be devoted to FIG. 3 wherein certain aspects of the B chip are shown. Specific details of generator assignment hereinafter to be discussed. Other details of the B-2 chip now to be discussed are to be found in the copending application of Harold O. Schwartz and Dennis E. Kidd filed June 20, 1978 under Ser. No. 917,313.

For a functional description of the B-2 chip, attention should be directed to FIG. 3 wherein there is shown a B-2 chip 82, identified on its face as B-2.sub.1 chip. A second B-2 chip 82a is identified on its face as B-2.sub.2 chip. These two chips are connected for parallel operation by five lines 84 interconnecting proper terminals or pins of the two chips. The data clock line 26 has an input into the chip 82, as do the system strobe line 48, and the serial data line 54 previously noted in connection with FIG. 1. Another input to the B-2 chip comprises a high frequency clock supplying high frequency oscillations on the order of four MHz at 86. This clock could be at a lower frequency as low as two or even one MHz. The B-2 chip has three generators 90, 92, and 94. Each of these generators is capable of generating any of the frequencies of 61 notes on the organ keyboard. Accommodation can be made readily to lesser or greater numbers of keys. Each generator comprises at least in part a divider of the high frequency input signal at 86, each dividing with a different ratio according to the given output tone. The drop clock signal on the line 88 causes a pulse to be dropped every so often so that none of the three generators is exactly the mathematically correct frequency, differing only by enough to avoid locking of the generators to one another in mathematically exact frequencies, whereby to present a better musical effect. The specifics of this function are to be found in the copending application of Anthony C. Ippolito and William R. Hoskinson filed June 20, 1978, under Ser. No. 917,296 now U.S. Pat. No. 4,196,651. A single B-2 chip can be used to produce three melody notes, which for less expensive instruments is sufficient. With the addition of a second B-2 chip as shown in FIG. 3 a total of six melody notes can be provided which is sufficient for most purposes. In theory twenty chips could be connected together to produce sixty generators which would cover all but one note of a sixty-one note keyboard to be played at one time. An additional B-2 chip could allow the sixty-first note to be played, but going to such extreme is quite unnecessary since under practical circumstances it is rare that one would want more than six melody notes to be played at one time. However, the capability is there, and with one or two chips redundancy of generators is greatly diminished or entirely eliminated, depending on one's viewpoint.

Envelope control of the frequencies being generated in the B-2 chip 82 is effected by three like sets of input controls 96 and capacitors 98, 100, and 102. This envelope control is detailed in the copending application of William R. Hoskinson filed June 20, 1978 under Ser. No. 917,308. The first such set is identified by numeral 104 and controls a one eighth duty cycle output wave. The second such control at set 106 is identified by numeral 106 and controls a 50% duty cycle output wave. The third set 108 controls a 50% duty cycle frequency steered output. More will be said about the frequency steering shortly hereinafter.

Within the bottom of the rectangle comprising the B-2 chip 82 there are shown three sets 110, 112, and 114 of keyers, each comprising keyer 1, keyer 2 and keyer 3. The frequency of each generator is assigned in accordance with the aforesaid Schwartz and Kidd application (attorneys docket number 688I). Each generator is keyed out of the chip by respectively numbered keyers. Thus, Generator #1 is keyed by means of the 3 keyers #1, etc.

A pulse output is provided at 116, and a pulse is outputed at this connection each time a new key is played. This pulse is of approximately 12 msec. duration. There is also an output 118 of eight foot pitch at a one eighth duty cycle. Next to that are shown outputs 120, 122, 124 and 126, all at 50% duty cycle, for, respectively, 16', 8', 4' and 2' organ voices. For example, if a 16' tone is to be played on the organ in accordance with setting of the function switches, no matter what key may be depressed on the keyboard, the 16' tone will be outputed at 120.

Next to that are seven output connections 128, 130, 132, 134, 136 and 140. The output of these respective connections is a 50% duty cycle which is frequency steered. In order to comprehend the frequency steering, attention should be directed to the fact that the first five pins, namely pins 128 through 136, will output a 16' voice, with one octave per pin or connection. Thus, the lowest octave of the organ will appear at output connection 128 in a 16' voice. This output connection serves only the lowest octave and no other. Similarly, on the 16' voice output connection 130 serves only the second octave, and no other. This continues through the pins up through 140. The advantage to this is that more precise filtering can be obtained for the desired harmonic content of the tone to be played. That is to say that there can be one filter per octave, rather than one filter for an entire 16' voice.

Similar explanation applies relative to the 8' voice which appears one octave at a time on pins 130 through 138. In like manner the 4' tones are produced on pins or connections 132 through 140.

Connection of various B-4 chips is shown in FIG. 4. Details of the B-4 chip are disclosed in the copending patent application of Harold O. Schwartz and William R. Hoskinson filed June 20, 1978 under Ser. No. 917,314. Thus, there are shown six B-4 chips 142, 142a, 142b, 142c, 142d, and 142e. Each of the B-4 chips covers one octave and one octave only. The number of six octaves here is sufficient to cover a 61 note keyboard. The first of the B-4 chips 142 is only accountable for one note, since the remaining five B-4 chips are sufficient to cover the five octaves for sixty keys. For smaller organs lesser numbers of B chips would be used. Each B-4 chip receives an input from the data clock 126, an input from system strobe 48, and also receives an input from the serial data line 54. The system strobe line 48 is also connected to the first B-4 chip at an input called chip position in which then sends a strobe signal over a line 144 to the second B-4 chip. This is continued serially with the same number 144 being used with the addition of suffixes a through d corresponding to the like B-4 chips with similar suffixes, to identify the octave placement of each chip.

Consideration has just been given as to the provision of six B-4 chips for an organ having a sixty-one note keyboard. Additional chips of the B family can be interconnected as is shown in FIG. 5. In this figure there are shown four B-4 chips 142, this being sufficient for a spinet organ having a keyboard of thirty-seven or forty-four notes. Some simplification of the drawing has been made in FIG. 5 to prevent crowding, but the input from the system strobe at 48 to the first B-4 chip is carried through successive B-4 chips through the interconnections 144. Serial data is entered from the serial data line 54 as before. In addition to the B-4 chips in FIG. 5 there is a like number of B-1 chips 146 which are controlled by the system strobe 48, and also have an input from the serial data line 54.

There are also two rows of B-2 chips 82, each row having four B-2 chips therein, and both supplied with serial data from the line 54, and strobed from the system strobe at 48. The five lines of interconnection 84 are as previously described under FIG. 3 with regard to the B-2 chips.

Specifics of the B-1 chip may be found in the corresponding copending application of Harold O. Schwartz and Dennis E. Kidd filed Nov. 11, 1978 under Ser. No. 962,981, while details as to the B-4 chip can be ascertained from the copending application of Harold O. Schwartz and William R. Hoskinson filed on June 20, 1978, under Ser. No. 917,314.

From the foregoing it will be seen that a very basic and simple organ could be made with just one B chip and an external counter for multiplexing. Better musical capabilities and little use of large scale integrated circuit chips is attained by providing one A-1 chip and four B chips of one sort or another. Improvement can be made as to features by adding an A-2 chip, and by adding other B chips in accordance with FIG. 5. The conventional 37 and 44 note spinet keyboards can be handled as well as can a full organ keyboard of sixty-one notes, simply by adding on additional B chips. It thus will be seen that a modular, expandable organ has been disclosed in which anything from a small and inexpensive organ up through a large and very expensive and comprehensive organ can be constructed by the addition of more modules or chips without the necessity of effecting any changes in the basic electronic construction of the organ.

The specific examples as herein shown and described are for illustrative purposes. Various changes will no doubt occur to those skilled in the art and will be understood as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.