JPS599914B2 - Electronic musical instrument sound source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound source device for an electronic musical instrument in which the duty cycle of a sound source signal can be set to an arbitrary value.

Generally, a square wave signal having a frequency corresponding to the pitch of a musical tone is used as a sound source signal for an electronic musical instrument.

This square wave sound source signal is formed by dividing the reference frequency signal in multiple stages using a divide-by-one circuit using flip-flops.

By the way, in order to enrich the timbre of the musical tones that are produced, it is preferable to use a sound source signal that contains as many harmonic components as possible. The take cycle was 1, and the timbre of the musical tones generated was limited because it did not contain any even-order harmonic components.

This invention was made in view of the above circumstances, and aims to obtain a sound source signal rich in harmonic components by digitally generating a sound source signal with a duty cycle set to an arbitrary value. . For this purpose, in the present invention, the output of a numerical signal generation circuit that sequentially generates numerical signals at a predetermined speed, and the output of a selected one of at least two storage circuits from which predetermined numerical signals are read out in correspondence with musical tone information. The output of the memory circuit is compared in a coincidence circuit, and a sound source signal is formed based on the coincidence signal from the coincidence circuit, and the memory circuit is sequentially switched every time the coincidence signal is generated. Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a sound source device for an electronic musical instrument according to the present invention.

In the shift register 1F, the output signals of two stages out of each stage output, for example, the two stages of the final stage, are applied to the input terminal of the shift register 1 via the exclusive OR circuit 2, and different numerical signals are applied. This forms a numerical signal generation circuit that sequentially generates . For example, shift register 5 register 1 has 9 stages, and now each stage is all "
1'', each stage of the shift register 1 outputs a one-layer numerical signal (as shown in Table 1) as a clock pulse φ1.

In this case, the frequency of the clock pulse φ1 is determined in accordance with the octave information of the generated musical tone.

That is, the clock pulse φ1 is obtained by adding the master clock pulse φ to a frequency dividing circuit 2n circuit 20 whose frequency division ratio is changed by octave information 0CT(n), as shown in FIG.
Master clock pulse φ is octave information 0CT(n)
is formed by frequency division corresponding to .

Therefore, from each stage of shift register 1, the above table 1
Numerical signals as shown in 2 are sequentially generated at frequencies corresponding to the octave information 0CT.

The output of each stage of this shift register 1 is applied to a matching circuit 3. On the other hand, note name information NOTE of the generating instrument is added to the read-only memories ROM1 and ROM2.

What is pitch name information NOTE? Each pitch name Cl, C#,...
. . . corresponds to B, and for example, one encoded in 4 bits can be used. Read-only memories ROM1 and ROM2 contain note name information NO.
A predetermined numerical value is read out corresponding to TE. This numerical value has the same number of bits as the numerical value generated from the shift register 1, and is determined according to the frequency of the tone corresponding to the note name information NOTE. Read only memory RO
The numerical signals read from M1 and ROM2 are applied to selection circuit 4. Selection circuit 4 is read-only memory ROM
1 and the output of the ROM 2, and switching of the selection circuit 4 is performed by the output of a flip-flop 5, which will be described later. For example, when the output of flip-flop 5 is 60'', read-only memory R
Select the output of OMl, and the output of flip-flop 5 is 6.
When the value is 1°, the output of the read-only memory ROM2 is selected. The numerical signal read from the read-only memory ROM1 or ROM2 selected by the selection circuit 4 is applied to the matching circuit 3.

The coincidence circuit 3 combines the numerical signals sequentially generated from the shift register 3 and the read-only memory ROM1 or RO.
It compares the numerical signal read from M2 and outputs a match signal (one pulse signal) if the two match. This coincidence signal is applied to the flip-flop 5 to change the state of the flip-flop 5, and is also applied to the reset terminal R of the shift register 1, resetting all stages to "1". As a result, the shift register 1 starts generating numerical signals again from the beginning. Further, the output of the flip-flop 5 is applied to a selection circuit 4, and the selection circuit 4 is switched depending on the state of the flip-flop 5. Figure 3 A, b
is a timing chart showing the relationship between the output of the matching circuit 3 and the output of the flip-flop 5. The numerical signals sequentially generated from the shift register 1 are compared with the numerical values read out from the read-only memory ROM1, and when the two match at time t1, the matching circuit 3 outputs a matching signal as shown in FIG. 3a. As a result, the output of the flip-flop 5 rises from 601 to 61'' as shown in FIG. The output of 1 is now compared with the numerical signal read from read-only memory ROM2,
When the two coincide at time T2, the third
A coincidence signal is output as shown in FIG. 3A, and the output of the flip-flop 5 falls from 6F to 60° as shown in FIG. As a result, the selection circuit 4 again compares the numerical signal read out from the read-only memory ROM1. At time T3, when the output of the shift register 1 matches the numerical signal read from the read-only memory ROM1, a match signal is output from the match circuit 3, and the output of the flip-flop 5 rises from 60" to 0F", and the selection circuit 4 selects read-only memory ROM2, and the output of shift register 1 is compared with the numerical signal read from read-only memory ROM2. Thereafter, the output of the flip-flop 5 alternately repeats the binary state of 60 and "11" and becomes a square wave signal as shown in FIG. 3b. The square wave signal output from the flip-flop 5 is determined by the numerical signal read out from the read-only memory ROM2, and the time when the level is 60'', e.g. from time t1 to time T2 in FIG. The time from time T2 to time T3 in FIG. 3b is determined by a numerical signal read from the read-only memory ROM1. Also, the clock pulse φ applied to the shift register 1,
determines the rate of generation of the numerical signal generated from shift register 1, so the frequency of the square wave signal output from flip-flop 5 also depends on the frequency of clock pulse φ1. That is, the frequency of the output square wave signal of the flip-flop 5 is the same as that of the read-only memories ROM1 and ROM2.
The value of the duty cycle of the output square wave signal is determined by the numerical signal read from the read-only memory ROM1 and the frequency of the clock pulse φ1.
It is determined by the value read from OM2. By the way, in this embodiment, as described above, the frequency of the clock pulse φ1 is determined according to the octave information 0CT, and the numerical signals to be read from the read-only memories ROM1 and ROM2 are determined according to the note name information NOTE.
Therefore, octave information 0C is obtained from Fritz flop 5.
A sound source square wave signal having a frequency corresponding to T and note name information NOTE can be obtained.

Furthermore, by appropriately setting the numerical values read from the read-only memories ROM1 and ROM2 to different values, the duty cycle can be set to any value other than 1. Note that in the above embodiment, the final second
A shift register was used in which the output of the stage was added to the input terminal via an exclusive OR circuit, but it was possible to select any stage from among the outputs of each stage of the shift register, not just the final two stages, and to exclude this output. It may also be applied to the input terminal via a logical OR circuit. Also, the output of a counter can be used instead of the shift register. As explained above, according to the present invention, it is possible to form a sound source square wave signal with a duty cycle of an arbitrary value, and as a result, musical tones of various tones can be generated.

In addition, since the sound source signal is digitally generated, the frequency of the generated sound source signal is accurate and accurate pitch can be obtained, and the same duty ratio can be achieved even for musical tones with different frequencies (pitches). It is something that can maintain the cycle.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the sound source device for an electronic musical instrument of the present invention, FIG. 2 is a block diagram showing an example of a clock pulse forming circuit in the same embodiment, and FIG. 3 is a timing chart in the same embodiment. It is. 1... Shift register, 3... Match circuit, 4... Selection circuit, 5... Flip-flop, 20... Frequency divider circuit, ROMl, RO
M2...Read-only memory.

Claims (1)

[Claims] 1. Selecting a numerical signal generation circuit that generates numerical signals that sequentially change over time at a predetermined speed, at least two memory circuits from which predetermined numerical signals are read out in correspondence with musical tone information, and one of the memory circuits. a matching circuit that compares the output of the numerical signal generating circuit with the numerical signal read out from the storage circuit selected by the selecting means and outputs a matching signal every time the two match; A sound source for an electronic musical instrument, comprising: a flip-flop that operates in response to a match signal from a match circuit to form a sound source signal; and means for switching the selection operation of the selection means every time a match signal is output from the match circuit. Device.