JP2679393B2 - Music synthesizer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a musical sound synthesizer suitable for use in musical sound synthesis of plucked string instruments, stringed instruments, and the like.

2. Description of the Related Art Conventionally, a device that synthesizes a musical tone of a natural musical instrument by simulating a sounding mechanism of the natural musical instrument has been known. As a musical sound synthesizer for string instrument sounds, a low-pass filter simulating the vibration loss of the string and a delay circuit simulating the propagation delay of the vibration in the string using a shift register were closed-loop connected and injected from the waveform memory. A technique for synthesizing a musical sound by circulating a musical sound waveform is known. In such a configuration, when an excitation signal such as an impulse is introduced into the closed loop circuit, the excitation signal circulates in the closed loop. In this case, the excitation signal makes a round in the closed loop for a time equal to the vibration period of the string, and the band is limited when passing through the low-pass filter. Then, a signal circulating in the closed loop is extracted as a tone signal of the stringed instrument.

According to such a tone synthesizer, by adjusting the delay time of the delay circuit and the characteristics of the low-pass filter, plucked instrument sounds such as guitars, percussion sounds such as pianos, etc.
Musical sounds similar to natural stringed instrument sounds can be synthesized. Further, the tone synthesis of a bowed instrument sound such as a violin is realized by connecting an excitation circuit for calculating vibration for exciting a string by a bow to the above-described closed loop circuit. This type of technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-40199 or Japanese Patent Publication No. 58-58679.

[Problems to be Solved by the Invention] However, in the conventional musical tone synthesizer, the signal circulating through the closed loop is taken out as the musical tone signal of the stringed instrument, and the rising edge of the output waveform taken out at this time is the feedback loop. Since the configuration is determined by the time constant, it is difficult to sharpen the rise of the output waveform, and the output waveform cannot be output at a constant level.
For example, there has been a problem that it is not possible to sufficiently control output rise (envelope control) and stabilize output amplitude.

On the other hand, in order to compensate for the above-mentioned drawbacks, for example, it is conceivable to increase the loop gain K. However, increasing this value causes problems such as oscillation of the loop and overflow of data in the loop, which is not preferable. .

The present invention has been made in view of the above problems,
It is an object of the present invention to provide a musical tone synthesizer capable of sufficiently controlling output rise control (envelope control) and stabilizing output amplitude without oscillating a loop circuit.

[Means for Solving the Problem] In order to solve the above-mentioned problems, in the present invention, a drive signal output means for outputting a drive signal, and a closed loop means excited by the drive signal and at least a delay means in a closed loop connection are provided. A tone synthesis apparatus for extracting a synthesized output of a musical sound from the closed loop means, the means for controlling the input level of the drive signal based on the envelope of the synthesized sound output of the closed loop means, It is characterized in that control means is provided so that the input level of the drive signal increases as the envelope of the combined output decreases.

In the present invention, the input level of the drive signal input from the drive signal output means to the closed loop means is controlled by the control means based on the envelope of the musical sound synthesis output of the closed loop means. Control is performed such that the smaller the value, the higher the input level of the drive signal.

Therefore, oscillation can be prevented without increasing the loop gain of the closed loop means, and rise control (envelope control) of musical sound synthesis output and stabilization of output amplitude can be sufficiently performed.

Further, if the input level of the drive signal is controlled according to the tone synthesis output itself of the closed loop means, the tone synthesis output of the closed loop means changes positively and negatively rapidly, and the input level of the drive signal is frequently changed. The problem arises that it will change. However, like the above configuration,
Such problems can be prevented by controlling the input level of the drive signal based on the envelope of the synthesized sound output of the closed loop means.

"Example" Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a musical sound synthesizer applied to an electronic musical instrument according to the present invention. In FIG. 1, the tone synthesis apparatus according to the present embodiment comprises a tone control information generator 1, a drive waveform generator 2, an envelope detector 3, a variable delay circuit 4, a filter circuit 5, an adder 6 and multipliers 7 and 8. It is composed of

The tone control information generator 1 outputs the coefficient K, COEF, EGPAR, α, β, etc. necessary for setting and controlling the control information in each part of the device, and also the signal F indicating the pitch and the signal KON indicating the start and end of sound generation. Is output. A drive waveform generator (corresponding to a drive waveform output circuit) 2 outputs a drive waveform having a function corresponding to a sounding operator described later.

The drive waveform generator 2 is configured to include, for example, a CPU and a drive waveform memory, and the drive waveform memory stores several kinds of drive waveforms. When the keyboard is operated, the CPU fetches the key code and touch information, and based on these, requests the drive waveform memory to output the drive waveform through the address counter, and the address counter drives the drive waveform memory based on the signal from the CPU. Of the drive waveform is automatically generated, and one of them is indirectly designated by giving the read start address from the CPU, and the drive waveform generated by the drive waveform memory is output.
The drive waveform generated by the drive waveform memory is the multiplier 8
Is injected into the closed loop circuit 11 described later via.

The variable delay circuit 4, the filter circuit 5, the adder 6 and the multiplier 7 constitute a closed loop circuit 11, and the closed loop circuit 11, the multiplier 8, the drive waveform generator 2 and the envelope detector 3 are delay feedback type as a whole. Sound source 12
Is composed. The delay feedback type sound source 12 is a sounding body having a predetermined resonance characteristic (for example, in the case of a piano,
It has a function imitating a sounding mechanism in which a sound equivalent to a piano string is excited by a sounding operator (for example, a hammer hitting a string) to generate a vibration propagating back and forth through the sounding body to synthesize a musical sound. . On the other hand, the closed loop circuit 11 is constituted by a circuit in which a filter for simulating vibration loss of the sounding body and a delay circuit for simulating vibration propagation delay in the sounding body are connected in a closed loop, and a synthetic output of musical sound is extracted from the closed loop circuit 11. Be done. That is, the variable delay circuit 4 changes its delay time (the number of delay stages) according to the pitch information F, and simulates the propagation delay of vibration in the sounding body (string or the like), and the filter circuit 5 uses the primary filter. Then, simulate the vibration loss of the sounding body. Further, the multiplier 7 controls the gain of the closed loop based on the loop gain control signal K from the tone control information generating section 1.

The envelope detector 3 has a function as an output detecting means for detecting the magnitude of the tone synthesis output of the closed loop circuit 11, and the multiplier (corresponding to the control means) 8 has a drive waveform based on the output of the envelope detector 3. The input level of the drive waveform input from the generator 2 to the closed loop circuit 11 is controlled.
For example, when the output of the envelope detector 3 is L (L is a value when the desired output level is [1]), the multiplier 8 is driven with a gain represented by the formula G = 1-L. The level of the drive waveform output from the waveform generator 2 is controlled and input to the closed loop circuit 11.

The control means is not limited to the above example, and may use logarithm as shown in FIG. 2, for example. That is, the second
In the figure, the control means 21 is an arithmetic unit 22 to 24 and an adder 25.
Composed of The arithmetic units 22 and 23 are linear / log converters for converting constants to logarithms, and the arithmetic units 24 are log / linear converters for converting logarithms to constants. Therefore,
When the control means 21 is used, the level control of the drive waveform is performed by logarithmic calculation. In this case, the drive waveform generator 2 may store the drive waveform as a logarithmic value in the memory.

On the other hand, the envelope detector 3 has a detailed configuration of the third embodiment.
As shown in the figure, it has an exclusive OR gate 31, a half adder 32, adders 33 to 35, multipliers 36 and 37, a delay circuit 38 and an output value conversion circuit 39. The tone synthesis output of the closed loop circuit 11 is supplied as an input signal to the exclusive OR gate 31. In this case, the input signal is supplied as an N-bit [2] complement expression, the absolute value of the input signal is taken by the NOR gate 31 and the half adder 32, and the output waveform thereof is shown in FIG. Note that this output waveform is based on sign inversion, for example,
It may be stored in a table and retrieved by table lookup. A smoothing filter 41 is configured by the adders 33 and 34, the multiplier 36, and the delay circuit 38, and the smoothing filter 41 smoothes the N-bit absolute value output output from the half adder 32. The smoothing filter 41 is a general filter, and for example, FIR, IIR or the like is possible. The output value conversion circuit 39 outputs the output of the smoothing filter 41 to the analog signal ENV.
The signal ENV in this case is in the range of 0 ≦ ENV ≦ 1. The multiplier 37 performs sensitivity adjustment for the signal ENV based on the inverted level adjustment signal β. The adjustment signal β is −
The value is in the range of 1 ≦ β ≦ 0. [1] is added to the output of the multiplier 37 by the adder 35, and finally the envelope detection output EVNVF is output from the envelope detector 3.

Next, the operation of the embodiment in the above configuration will be described.

When performance information such as key information is supplied to the musical tone control information generating section 1 in response to a key depression operation on the keyboard, the generating section 1 sends various control signals to each section of the circuit shown in FIG. 1 based on the performance information. Then, the drive waveform from the drive waveform generator 2 is output to the multiplier 8
Is input to the closed loop circuit 11 via the, and this drive waveform circulates in the closed loop. In this case, the drive waveform makes one round in the closed loop at a time equal to the vibration period of the string, and the signal circulating in this closed loop is taken out as the musical tone signal of the musical instrument.

Here, in the present embodiment, the level (envelope) of the musical tone signal that circulates in the closed loop and is extracted to the outside is detected by the envelope detector 3, and the detection result is output to the multiplier 8. Specifically, the envelope detector 3
The absolute value output section and the smoothing filter 41 are vertically connected, and are output to the multiplier 8 as a coefficient value within 0 to 1 according to the change of the level envelope of the tone signal as shown in FIG. In this case, the control output ENVF to the multiplier 8 changes in the range of 1 to 0 with respect to the change of the envelope ENV of the input signal (tone signal) from 0 to 1, and the contribution of the input envelope ENV to the control output ENVF. Is adjusted by the level adjustment signal β described above. Therefore, the input level of the drive waveform input from the drive waveform generator 2 to the closed loop circuit 11 is controlled by the multiplier 8, and eventually the amplitude of the drive waveform input is controlled while monitoring the output waveform of the closed loop circuit 11. It will be. This makes it possible to sharpen the rising edge of the musical sound output waveform without increasing the loop gain K, unlike the conventional case. As a result, the musical sound output waveform can be output at a constant level, and, for example, output rise control (envelope control) and output amplitude stabilization can be sufficiently performed. Also, since it is not necessary to increase the loop gain K, oscillation of the loop and overflow of data in the loop are prevented.

It is also possible to further finely control the musical sound output controlled to a constant level by the envelope generator. Further, the loop gain K may be increased within the range where the musical sound output is controlled to a constant level. For example,
The range is K <1, and strictly speaking, the total gain G including the filter may be in the range | G | <1.

Further, the present invention is not limited to the above embodiment, and various modifications as described below are possible.

(I) Envelope detection may output only one polarity of the input signal by half-wave rectification instead of absolute value output.

(II) In addition to the primary filter shown in FIG. 3, the filter for envelope detection may be of another type, for example, a filter including filter feedback or a digital IIR or APF that is not a linear phase filter, or A higher order filter may be used.

(III) Instead of the multiplier 8 as the control means, for example, a logarithmic filter (EXP filter) is used, and the characteristic of the filter is changed according to the result of the level detection in the closed loop by the envelope detector to control the drive waveform input level. You may do it.

[Advantages of the Invention] According to the present invention, it is not necessary to increase the loop gain of the closed loop means, and it is possible to prevent the oscillation of the loop and the overflow of the data in the loop while controlling the rising edge of the musical sound synthesis output (envelope control) and the output amplitude. Can be sufficiently stabilized. If the input level of the drive signal is controlled according to the tone synthesis output itself of the closed loop means, the tone synthesis output of the closed loop means changes positively and negatively and the input level of the drive signal also changes frequently. However, in the present invention, the input level of the drive signal is controlled based on the envelope of the musical sound synthesis output of the closed loop means, and there is an effect that such a problem can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a diagram showing a circuit of a modification of the control means in the same embodiment, and FIG. 3 is a detailed view of the envelope detector in the same embodiment. FIG. 4 is a diagram showing the circuit, FIG. 4 is a diagram for explaining the absolute value output of the envelope detector in the same embodiment, and FIG. 5 is a waveform diagram for explaining the envelope detection in the same embodiment. 2 ... Drive waveform generating section, 3 ... Envelope detector (control means), 8 ... Multiplier (control means), 11 ... Closed loop circuit, 12 ... Delayed feedback type sound source.

Claims (1)

(57) [Claims] 1. A musical tone synthesizing apparatus having driving signal output means for outputting a driving signal, and closed loop means excited by the driving signal and having at least a delay means connected in a closed loop, wherein a synthetic output of musical sound is taken out from the closed loop means. A means for controlling the input level of the drive signal based on the envelope of the tone synthesis output of the closed loop means, wherein the input level of the drive signal increases as the envelope of the tone synthesis output of the closed loop means decreases. A musical tone synthesizing device, characterized in that a control means for controlling is provided.