1. Field of the Invention
The present invention relates to electronic musical instruments, and more particularly, to electronic musical instruments capable of simulating the sound of conventional non-electronic musical instruments with high fidelity.
2. Prior Art
There is known a conventional electronic musical instrument comprising a PCM (Pulse Code Modulation) tone generating device (hereafter referred to as a tone generating device (1)) which reads pulse-code-modulated waveform data from a waveform memory based on a clock corresponding to MIDI (Musical Instrument Digital Interface) data generated in response to the operation of, for example, a keyboard by a performer. Such a conventional electronic musical instrument comprises a plurality of sound production channels, for example, 16 sound production channels, and each of these sound production channels independently produces sound by means of timesharing in response to the above MIDI data. For example, one sound production channel produces sound with the tone color of a piano at one timing and another sound production channel produces sound with the tone color of a violin at another timing.
Furthermore, physical model tone generating devices (hereafter referred to as tone generating devices (2)) are conventionally known which synthesize tones which effectively simulate the sound of a conventional non-electronic musical instrument by simulating the sound production algorithm in the target non-electronic instrument. Such a device is disclosed in U.S. Pat. No. 4,984,276.
One example of a linear portion of the above conventional tone generating device (2) is shown in the block diagram of FIG. 9. In this figure, an input terminal 1 is provided, to which an excitation signal waveform data made up of a large number of different high frequency components such as an impulse waveform is supplied. The excitation signal waveform data supplied via the input terminal 1 is supplied to the closed loop circuit via first input terminals of adders 2 and 3. The adder 3 adds the excitation signal waveform data and the output data read from an input memory 5 (MEMORY 2) which delays an input data for the desired time. The output data from the adder 3 is supplied to a multiplier 6 which multiplies it by a multiplicative coefficient C2. The output data from the multiplier 6 is supplied to a first input terminal of an adder 8. The output data from the adder 8 is stored in a temporary memory 9 (TL2) and supplied to a multiplier 11. The temporary memory 9 delays an input data, namely, the output data from the adder 8, for the desired time. The multiplier 11 multiplies an input data, namely, the output data from the adder 8, by a multiplicative coefficient r2. The data read from the temporary memory 9 is supplied to a multiplier 10. The multiplier 10 multiplies an input data, namely, the data read from the temporary memory 9, by a multiplicative coefficient 1-C2. The output data from the multiplier 10 is supplied to a second input terminal of the adder 8. The adder 8 adds the output data from the multiplier 6 and the output data from the multiplier 10. Each of elements 8 through 10 described above together form a low pass filter (LPF) 12. The output data from the multiplier 11 is stored in an input memory 4 (MEMORY 1) which delays it for the desired time.. The data read from the input memory 4 is supplied to a second input terminal of the adder 2.
The adder 2 adds the excitation signal waveform data and the data read from the input memory 4. The output data from the adder 2 is supplied to a multiplier 7 which multiplies it by a multiplicative coefficient C1. The output data from the multiplier 7 is supplied to a first input terminal of an adder 13. The output data from the adder 13 is stored in a temporary memory 14 (TL1) and supplied to a multiplier 16. The temporary memory 14 delays an input data, namely, the output data from the adder 13, for the desired time. The multiplier 16 multiplies an input data, namely, the output data from the adder 13, by a multiplicative coefficient r1. The data read from the temporary memory 14 is supplied to a multiplier 15. The multiplier 10 multiplies an input data, namely, the data read from the temporary memory 14 by a multiplicative coefficient 1-C1. The output data from the multiplier 15 is supplied to a second input terminal of the adder 13. The adder 13 adds the output data from the multiplier 7 and the output data from the multiplier 15. Each of elements 13 through 15 described above together form a low pass filter (LPF) 17. The output data from the multiplier 16 is stored in the input memory 5. The data read from the input memory 5 is supplied to a second input terminal of the adder 3.
Because the above conventional tone generating device (2) consists of a digital signal processor (DSP), it can synthesize various tones which effectively simulate the sound of conventional non-electronic musical instruments by simulating the various algorithms of sound production in the target non-electronic instruments by changing the microprogram (for example, see FIG. 10) used in the DSP. The above conventional tone generating device (2) as shown in FIG. 9 is an example of a tone generating device which synthesizes tone which effectively simulates the sound of a stringed instrument by simulating the sound production algorithm in the stringed instrument. An example of another type of tone generating device which synthesizes tones which effectively simulates the sound of another non-electronic musical instruments, for example, wind instruments, by simulating the sound production algorithm in the target non-electronic musical instruments, has been disclosed in Japanese Patent Application Laid-open Publication No. 2-280196.
In the above conventional electronic musical instrument comprising the above conventional tone generating device (1), a tone color number as well as performance information such as tone pitch and touch are supplied to the tone generating device (1) every key-on. Accordingly, if a performer designates tone color at each sound production, each of the sound production channels of the tone generating device (1) directly access the corresponding area of the waveform memory and read waveform data from it. Thus, as stated above, it is an easy matter for one sound production channel to produce sound with the tone color of a piano at one timing and to produce sound with the tone color of a violin at the next timing by means of timesharing.
In contrast, in the above conventional electronic musical instrument comprising the above conventional tone generating device (2), in the case of changing tone color at each key-on, there is a necessity either to supply a microprogram to the sound production channel at each key-on or to previously store a plurality of microprograms in each sound channel. Since the microprogram as shown in FIG. 10 is the microprogram corresponding to very a fundamental circuit construction as shown in FIG. 9, it does not take long to supply this microprogram to the sound production channel at each key-on. However, since the microprogram which accurately simulates the sound production algorithm in the target non-electronic musical instruments consists of a large number of data, when it is supplied to the sound production channel at each key-on, there is a drawback in that the key-on response is reduced due to the limitation on the data transmitting rate. In the case where previously storing a plurality of microprograms in each sound channel, there is a drawback in that the use efficiency of memory becomes lower and the system become expensive because great deal of memory is necessary.