Tone Generator Having a Variable Number of Channels With a Variable Number of Operating Units

This invention relates to a tone signal generation device and, more particularly, to a device capable of generating a tone signal of a desired tone color by performing a tone generating operation (computation) such as a frequency modulation operation and amplitude modulation operation. More particularly, the invention relates to a tone signal generation device in which a plurality of tone generation channels are provided for enabling simultaneous sounding of plural tones and which is capable of changing the maximum number of tones simultaneously produced depending upon a tone or tones to be produced.

A basic system for generating a tone signal by using a frequency modulation (hereinafter abbreviated as FM) operation in the audio frequency range is disclosed in the U.S. Pat. No. 4,018,121. A basic system for generating a tone signal by using an amplitude modulation (hereinafter abbreviated as AM) operation in the audio range is disclosed in Japanese Patent Publication No. 29519/1983. Known also in the art is an electronic musical instrument which includes a limited number of tone generation channels wherein the sounding of a tone for a depressed key is assigned to any of the tone generation channels whereby different tones corresponding in number to the number of the tone generation channels can be simultaneously produced (e.g., the U.S. Pat. No. 3,882,751).

It is also known to employ one of the above described basic operation systems (FM or AM) as a tone generation system in each of such a plurality of tone generation channels and to sound plural tones generated by such operation systems simultaneously. In such prior art electronic musical instruments, the number of tone generation channels is fixed and it is not possible to change this number depending upon the situation.

In a tone generation system employing the above described operation systems, one or more basic operation units (or operation channels) are used in one tone generation channel and operation parameters in each operation unit are suitably selected to generate a tone signal of a desired tone color. In this case, the more the operation units are used, the more various and complex tone color control one can realize. Therefore, the number of basic operation units per one tone generation channel should preferably be large if the tone color or quality of a tone to be achieved is important. Further, there is a case in which a sufficient number of basic operation units are required depending upon the tone color or performance mode selected. On the other hand, there is also a case in which the number of the operation units per one tone generation channel need not be large whereas the number of tones which can be sounded simultaneously should be large. For satisfying the former requirement, the number of the operation units (operation channels) per one tone generation channel must be sufficiently large whereas for satisfying the latter requirement, the number of the tone generation channels must be large. Therefore, there arises the problem that it requires a large and costly device to satisfy both these requirements. Although a plurality of operation units can be realized by using a single basic operation circuit on a time shared basis, the increase in the number of operation units obliges an increase in the time division clock rate which result in a rise in the manufacturing cost. Further, aside from such problems, many unused operation units (operation channels) will be wasted in such a device having a large number of tone generation channels and a large number of operation units when a tone color or a performance mode which does not required a large number of operation units per one tone generation channel has been selected.

It is, therefore, an object of the present invention to provide a tone signal generation device capable of generating plural tones simultaneously by the operation type tone generation system, which utilizes a limited number of operation channels (operation units) efficiently and without waste and which changes the maximum number of tones that can be sounded simultaneously as desired.

For achieving the above described object, the tone signal generation device of the present invention comprises tone generation operation means including a predetermined number of operation channels for tone signal computation and generating a tone signal by performing a specific tone generation operation employing one or more of said operation channels for one tone generation channel, wherein a plurality of said tone generation channels are established thereby enabling generation of plural tones, mode selection means for selecting one mode for among a plurality of modes, and channel establishing means for dividing said operation channels into plural groups in a predetermined manner in accordance with the mode selected by said mode selection means and establishing said tone generation channels so that each is constituted by one of the operation channel groups, the number of said groups being different depending upon the selected mode. The number of the tone generation channels in said tone generation operation means and the number of operation channels in each group can therefore be changed in accordance with the selected mode.

In the accompanying drawings,

FIG. 1 is a functional block diagram showing the basic organization of the invention;

FIG. 2 is a block diagram showing the hardware construction of an electronic musical instrument incorporating an embodiment of the invention;

FIG. 3 is an example of a manner of establishing channels in each of two modes in the embodiment of FIG. 2;

FIG. 4 is a diagram showing an example of the structuring of the memory in the data and working RAM shown in FIG. 2;

FIG. 5 is a flow chart schematically showing an example of a main routine of a program executed by a microcomputer unit in FIG. 2;

FIG. 6 is a flow chart showing an example of a panel scanning subroutine executed in the panel operator scanning processing of FIG. 5;

FIG. 7 is a flow chart showing an example of a key scanning subroutine executed in the key scanning processing of FIG. 5;

FIG. 8 is a block diagram showing an example of an interface for the embodiment of FIG. 2;

FIG. 9 is a time charge showing an example of the relationship between a plurality of time division time slots corresponding to thirty-two operation channels and a plurality of tone generaton channels during a normal mode and an ABC mode corresponding to the respective time slots and also showing an example of timing signal;

FIG. 10 is a block diagram showing an example of the internal construction of a tone generator in the embodiment of FIG. 2;

FIGS. 11 (a)-(d) are time charts showing an example of the operation of the circuit of FIG. 10; and

FIG. 12 is a schematic block diagram showing an example of a manner of connecting operation channels in one tone generation channel.

The basic construction of this tone signal generation device will be described with reference to FIG. 1. Tone generation operation means 10 includes operation channels OP1-OPx of a specific number x. The respective operation channels OP1-OPx each implement a respective basic computing operation of a predetermined tone generation operation. A tone signal is generated by performing the predetermined tone generation operation employing one or more operation channels OP1-OPx for one tone generation channel. A plurality of such tone generation channels employing one or more operation channels OP1-OPx are established by a channel establishing means 11 and simultaneous generation of plural tones thereby is made possible. The channel establishing means 11 establishes the tone generation channels in the tone generation operation means 10 in different modes in accordance with a mode (e.g., either a first mode or a second mode) selected by a mode selection means 12. In the first mode, the operation channels OP1-OPx are divided into N groups in a predetermined manner and N tone generation channels are established corresponding to the respective N groups. In the second mode, the operation channels OP1-OPx are divided into M (N.noteq.M) groups in a predetermined manner and M tone generation channels are established in correspondence to the respective M groups. In this manner, the number of tone generation channels in the tone generation operation means 10 can be switched to N or M in accordance with the selected mode. The number of modes is not limited to two.

Thus, the operation channels OP1-OPx of a specific number x are divided into N or M groups depending upon the selected mode (the number of the operation channels within each group is not necessarily equal to that of the other groups) and the tone generation channels are established according to these groups.

Accordingly, the number of tone generation channels can be changed so that the maximum number of tones which can be sounded simultaneously can be suitably changed by changing modes. In a case where a tone of a high quality is to be obtained or a complex tone color control is to be performed, i.e., where a relatively large number of operation channels need to be used for one tone generation channel, the grouping of the operation channels is established to serve this purpose and the mode is changed to one in which the number of the tone generation channels is relatively decreased. Conversely, in a case where a relatively simple tone color control is to be performed or the number of the tone generation channels is to be relatively increased, i.e., where the number of the operation channels used for one tone generation channel can be relatively small, the grouping of the operation channels is established to serve this purpose and the mode is changed to one in which the number of the tone generation channels is relatively increased.

In this manner, operation channels of a limited number can be utilized efficiently and without waste so as to increase or decrease the maximum number of tones to be sounded simultaneously as desired whereby the two requirements of improvement in tone quality and an increase in the number of tones to be sounded simultaneously can be selectively realized by using a device of a limited construction.

For example, in FIG. 1 the channel establishing means 11 includes a tone assigner means 11a and a parameter supply means 11b as shown. The tone assigner means 11a assigns a tone to be generated to N or M tone generation channels established in accordance with the mode selected by the mode selection means 12. In other words, the number of the tone generation channels which are subjected to the assignment by the tone assigner means 11a increases or decreases depending upon the mode. Information representing the tone pitches of tone which have been assigned to the respective tone generation channels is supplied to the tone generation operation means 10 in accordance with operation channel groups corresponding to the tone generation channels. The parameter supply means 11b supplies operation parameters for respective operation channels in the N or M tone generation channels established in accordance with the selected mode. The tone generation operation means 10 establishes operation algorithms and operation coefficients in response to the operation parameters supplied to the respective operation channels and, in accordance with these operation algorithms and operation coefficients, and also with the information representing the tone pitches of the tones assigned to the respective tone generation channels, performs the tone generation operation (computation) and generates tone signals from the respective tone generation channels.

An embodiment of the invention will not be described in detail with reference to the subsequent drawings.

FIG. 2 is a block diagram schematically showing a hardware construction, i.e., an electrical circuitry, of a keyboard type electronic musical instrument which is an embodiment of the tone signal generation device according to the invention. In this embodiment, there is provided a tone generator 13 corresponding to the above described tone generation operation means 10. In the example shown, the tone generator 13 comprises a basic operation circuit 13a which is preferably of the FM type, but can also be of the AM type. A plurality of operation channels of a specific number x (in the present embodiment, x is assumed to be 32) are provided in the form of time division time slots by using this basic operation circuit 13a on a time shared basis. For distinguishing the operation channels from the tone generation channels, the operation channels will be referred to as "operation time slots" or "operation slots" in the following description and the term "channel" will be used to designate the tone generation channels unless otherwise particularly specified.

This electronic musical instrument comprises a microcomputer section COM including a CPU (central processing unit) 14, a program ROM (read-only memory) 15 and a data and working RAM (random-access memory) 16. A key switch circuit 17 consisting of keys in a keyboard, a panel operation switch section 18 and a voice parameter memory 19 are connected to the microcomputer section COM through a bus 20. The tone generator 13 is connected also to the microcomputer section COM through an interface 21 and the bus 20. By controlling this microcomputer section COM, key switches in the key switch circuit 17 are scanned, the depression or release of keys are thereby detected and a process for assigning the generation of the tone of the depressed key to any particular one of a plurality of tone generation channels is effected. Further, by controlling the microcomputer section COM, the operation states of various switches and operation knobs in the panel operation switch section 18 are scanned and processings according to the results of the scanning (including a processing corresponding to the channel establishing means 11 in FIG. 1) are executed.

The panel operation switch section 18 comprises an automatic bass/chord performance (hereinafter sometimes referred to as ABC) selection switch 22, a melody tone color selection swtich 23, a chord tone color selection switch 24, a bass tone color selection switch 25 and various other switches controlling tone color, tone level and tonal effects, and display means associated to these switches.

The ABC selection switch 22 corresponds to the mode selection means 12. When the automatic bass/chord performance is not selected by this switch 22, the device is in a first mode (referred also as a "normal mode") and when the automatic bass/chord performance is selected by the switch 22, the device is in a second mode (referred also to as the "ABC mode"). The tone color selection switches 23, 24 and 25 are provided for respectively selecting tone colors for playing melody tones, bass tones and chord tones.

In the present embodiment, the keyboard is constructed as a single-stage keyboard. In the normal mode, all keys are used for playing melody tones whereas in the ABC mode, a key range on the higher side of a predetermined key is used as a melody key range and a key range on the lower side of the predetermined key as an accompaniment key range. In the normal mode, a tone corresponding to a key depressed in the keyboard is generated with a melody tone color imparted thereto in accordance with the key depressing operation. In the ABC mode, a tone corresponding to a key depressed in the melody key range is generated with a melody color imparted thereto in accordance with the key depressing operation while a base tone and a chord tone are formed in accordance with a key depressed in the accompaniment key range, and the tones thus imparted with the melody tone, the bass tone and the chord tone are generated in accordance with an automatic tone generation timing.

The voice parameter memory 19 consists, for example, of a ROM and stores parameters (hereinafter referred to as voice parameters) necessary for producing various tone colors selectable by the tone color selection switches 23-25 in correspondence to these tone colors. Voice parameters corresponding to the tone colors selected by the respective switches 23-25 are read out from this voice parameter memory 19. The read out voice parameters are supplied to the tone generator 13 as a part of the operation parameters.

FIG. 3 shows an example of a channel establishment in each mode. The contents of the channel establishment are programmed by the microcomputer section COM so as to become those shown in FIG. 3 in accordance with the mode selected. In the normal mode, the thirty-two operation channels i.e., operation time slots, are divided into eight groups each consisting of four operation channels. Eight tone generation channels CH1-CH8 are designated by the eight groups. An arrangement is made so that a tone signal will be generated with a melody tone color common through all of the eight tone generation channels. In the ABC mode, six tone generation channels CH1-CH6 are provided corresponding to six groups each consisting of four operation channels and four tone generation channels CH7 -CH10 are provided in corespondence to four groups each consisting of two operation channels. In this case, five of the tone generation channels CH1-CH5 are used for generating tones having the melody tone color and four of the tone generation channels CH7-CH10 are used for generating tones having the chord tone color. In the foregoing manner, eight tone generation channels are used in the normal mode whereas ten tone generation channels are used in the ABC mode. Alternatively stated, the groups for the tone generation channels CH7 and CH8 each consisting of four operation channels (7, 15, 23, 31) and (8, 16, 24, 32) are respectively divided in half thereby respectively providing four groups each consisting of two operation channels. As a result, four tone generation channels CH7-CH10 are provided in correspondence to the four groups each consisting of two operation channels (7,23), (8,24), (15,31) and (16,32).

In accordance with the differences in the contents of the channel establishment, depending upon the mode, contents of the key assigning processings in the microcomputer section COM become different depending upon the mode and the manner of supplying the voice parameters becomes also different depending upon the mode. Data and voice parameters corresponding to the tone pitches of tones assigned to the tone generation channels CH1-CH8 or CH1-CH10 which vary depending upon the mode are supplied from the microcomputer section COM to the tone generator 13 through the interface 21. The tone generator 13 performs an eight-channel type of ten-channel type tone generation operation in accordance with the data supplied from the microcomputer section COM. The generated tone signal is supplied to a sound system 26.

FIG. 4 shows an example of a memory structure in the data and working RAM 16. An ABC register stores a signal indicating whether the selected mode is the ABC mode or not. When this signal is "1", the selected mode is the ABC mode and when the signal is "0", the selected mode is the normal mode. Contents of this ABC register are switched by operation of the ABC selection switch 22. A UKTC register stores data (a melody tone color code UKTC) representing a melody tone color selected by the melody tone color selection switch 23. An LKTC register stores data (a chord tone color code LKTC) representing a chord tone color selected by the chord tone color selection switch 24. A PKTC register stores data (a bass tone color code PKTC) representing a bass tone color selected by the bass tone color selection switch 25. An LKKC memory stores a key code of a key depressed in the accompaniment key range (an accompaniment key range code LKKC). A normal mode key assignment memory 27 stores a key code KC and a key-on signal KON of a key which has been assigned to one of the tone generation channels CH1-CH8 for the melody tone color in the normal mode. An ABC mode key assignment memory 28 stores a key code KC and a key-on signal KON of a key which has been assigned to one of the tone generation channels CH1-CH5 for the melody tone color in the ABC mode.

An example of the program executed by the microcomputer section COM will be be described. FIG. 5 schematically shows the main routine of the program. In "panel operation switches scanning processing", respective switches in the panel operation switch section 18 are scanned and a predetermined processing is executed in accordance with results of the scanning. In this processing, a panel scanning subroutine PSUB as shown in FIG. 6 is executed. In "key scanning processing", respective keys in the key switch