JPS6154238B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an envelope control method for an electronic musical instrument that reads out a sine wave or a cosine wave according to a scale frequency to generate a musical tone.

In recent years, it has become possible to construct the main circuits of electronic musical instruments using digital technology. When generating musical tones using such digital technology, the waveform is stored in memory in advance and read out using a clock that corresponds to the scale frequency, or the readout clock is set at a constant frequency and phase for all scales. A method is used in which a musical tone is generated by changing the angle according to the scale frequency and reading it out.

Then, in the memory, one cycle of a waveform of a natural musical instrument is sampled and stored, or a waveform of a predetermined function, such as a sine wave, is stored.

However, when generating musical tones digitally as described above, in order to control the envelope (volume envelope), a multiplier must be used to multiply the binary data representing the waveform by the binary data representing the envelope. I need.

However, no matter what arithmetic method is used, such a multiplier requires very large hardware, which is inconvenient for integrating the circuits of electronic musical instruments. In order to correctly calculate the controlled peak value, it is necessary to obtain data of lower bits than the required number of bits, which has the drawback of being extremely complicated.

The present invention has been made in view of the above points, and is an electronic musical instrument that reads sine waves or cosine waves according to scale frequencies and generates musical tones. It reads out two waveforms that are opposite to each other and have the same amount of phase shift, and synthesizes the two read out waveforms to obtain an output. The purpose of this invention is to provide an envelope control method for electronic musical instruments that performs envelope control on waves.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a main circuit diagram of this embodiment. In the figure, 1 is a keyboard on which a plurality of performance keys are arranged. The keyboard 1 generates key codes corresponding to the operated performance keys. For example, the key code is a code indicating the octave and note (scale) of the performance key.

And this key code is frequency information conversion
Supplied to ROM2. This frequency information conversion ROM
2 stores frequency information (that is, information indicating a phase angle) corresponding to the key code, and this frequency information is sent to an accumulator 3 as an accumulation command (the clock φ will be described later). Accumulate each time.

For example, 6-bit data is supplied from the accumulator 3 to the A input terminal (A ₀ -A ₅ ) of the adder 4. On the other hand, the B input terminal (B ₀ ~
_B5 ) includes envelope information generating circuit 6 from envelope information generating circuit 5.
Bit data is _supplied through exclusive OR gates _60-65 . Further, the carry input terminal cin of this adder 4 is supplied with a clock φ.

The envelope information generating circuit 5 is supplied with envelope control commands, such as on/off information of performance keys on the keyboard 1 or ADSR (Attack Decay Caste Release) information set in advance by a switch. 6-bit data for envelope control according to the information is given to the exclusive OR gates ₆₀ to ₆₅ . Note that a clock φ is applied to one end of the exclusive OR gates ₆₀ to ₆₅ .

Therefore, when this clock φ is at the "0" level, the adder 4 adds the 6-bit data given from the A input terminal and the B input terminal, and adds the 6-bit data given from the S output terminal (S ₀ to S ₅ ). Output the resulting data as bit data. On the other hand, when the clock φ is at the "1" level, the adder 4 receives the 6-bit data given from the A input terminal and the B
Data obtained by inverting the level of each bit of the 6-bit data provided from the input terminal and adding "+1" to the value, that is, data obtained by inverting the sign of the data provided from the B input terminal (2's complement representation)
and outputs the resulting data as 6-bit data from the S output terminal.

The 6-bit data output from the adder 4 is then given to the sine wave ROM 7, which generates a sine wave.
Specify the address of ROM7. this sine wave
In the ROM 7, the peak value (amplitude value) of a sine wave as shown in FIG. 2 is stored divided into 2 ⁶ (=64) sample points. And this sine wave ROM
, 6-bit data (D ₀ to D ₅ ) is output as a peak value. That is, the most significant bit (D ₅ ) of the output is a sign bit, and the second to lowest bits (D ₄ to D ₀ ) are bits indicating data below the decimal point.

This data is then applied to the A input terminals (A ₀ -A ₅ ) of the accumulator 8 and is accumulated. Incidentally, this accumulator 8 is reset at the timing of the rising edge of the signal obtained by inverting the clock φ by the inverter 9, that is, the clock. From this accumulator 8, 7-bit data is output from output terminals S (S ₀ -S ₆ ). That is, of this 7-bit data, the most significant bit (S ₆ ) is the sign bit, the second bit (S ₅ ) is the ^20th place bit, and the third to lowest bits (S ₄ to _{S 0} ) are the decimal point. This bit indicates the following data.

The 7-bit data output from the accumulator 8 is read into the latch 10 at the timing of the rising edge of the clock, and the output data is given to the D/A converter, converted into an analog signal, and sent through the acoustic conversion circuit. The sound will be emitted.

Next, the operation of this embodiment will be explained. First of all,
The above-mentioned clock φ and its inverted clock (accumulation command) will be explained with reference to FIG. This clock φ is a clock that alternately inverts the "0" level and the "1" level as shown in FIGS. 3a and 3b. For convenience of explanation, the time when the clock φ is at the "0" level will be referred to as timing _t0 , and the time when the clock φ is at the "1" level will be referred to as the timing _t1 .

Therefore, as shown in FIG. 3c, the circuit shown in FIG. 1 operates in a time-sharing manner at two timings. That is, the accumulator 3 adds frequency information corresponding to the operating key every time the accumulation command becomes "1", and applies the accumulation result data to the adder 4.

In the adder 4, the data from the envelope information generation circuit 5 is directly supplied from the B input terminal at timing _t0 , and is therefore added to the data from the A input terminal. Further, at timing _t1 , as described above, the data from the envelope information generation circuit 5 is supplied to the B input terminal with its sign inverted, and therefore, the adder 4 inputs this data and the data from the A input terminal. are added. The addition result data is then applied to the sine wave ROM 7.

Therefore, the sine wave ROM 7 is generally addressed differently at two timings, t ₀ and t ₁ , so that the data read from this sine wave ROM 7 at each timing is accumulated by the accumulator 8 . calculated.

The cumulative result is then latched in latch 10 at the rising edge of the clock.

Expressing the above explanation using a mathematical formula,
It will look like this: That is, the peak value read from the sine wave ROM 7 at timing t ₀ is sin2πa+b/2 ⁶ = sin(a+b)π/32...Equation (
1). Note that "a" is the data given to the A input terminal of the adder 4, and "b" is the data given to the A input terminal of the adder 4, and "b" is the data given to the exclusive OR gate ₆₀ to 65 from the envelope information generation circuit _5.
This is the data applied to.

Moreover, the peak value read from the sine wave ROM 7 at timing _t1 is sin2πa-b/2 ⁶ = sin(a-b)π/32...Equation (
2).

Therefore, the output of the accumulator 8 is sin2πa+b/2 ⁶ +sin2πa−b/2 ⁶ =2sinπ/32a cosπ/32b Equation (3).

Therefore, it is clear that envelope control can be performed by the data supplied to the B input terminal of the adder 4. That is, the envelope control value in that case is 2cosπ/32b...Equation (4).

Next, envelope control will be specifically explained with reference to FIGS. 4A to 4C. First, when the key is on and no waveform is being output, the envelope information generating circuit 5 outputs data "16". Therefore, at the timing of each _t0 , the data applied to the A input terminal of the adder 4 is increased by "+16". Therefore, for example, if the data applied to the A input terminal is "0", the output data is "16" is supplied to the sine wave ROM 7 and addressed.
On the other hand, at the timing of each _t1 , data obtained by adding "-16" to the data given to the A input terminal of adder 4,
Therefore, for example, when the data applied to the A input terminal is "0", the output data "64-16=48" is supplied to the sine wave ROM 7 and addressed.

Figure 4A shows the state. Figure 1 shows the data output from the sine wave ROM 7 at timing t ₀ , and Figure 4A shows the data output from the sine wave ROM 7 at timing t _1.
It shows data output from ROM7. In this way, since the phase of FIG. 4A 1 and FIG. It turns out.

Then, from this state, the envelope information generating circuit 5 gradually decreases the data supplied to the exclusive OR gates ₆₀ to ₆₅ from "16", thereby increasing the amplitude of the output waveform. For example, in FIG. 4B, the exclusive OR gates 6 ₀ to
6 shows each output waveform when the data supplied to ₅ is "11". Figure 1 shows the data output from the sine wave ROM 7 at timing t ₀ , and Figure 2 shows the sine wave data output from the sine wave ROM 7 at timing t ₁ . The data output from the ROM 7, and FIG. 3 shows the output data from the latch 10.

Furthermore, if the data supplied to the B input terminal of the adder 4 is reduced to "0", the data in FIGS. 4C, 1 to 3
As shown in , at timing t ₀ , the sine wave ROM7
The data read from the sine wave ROM 7 and the data read from the sine wave ROM 7 at timing _t1 are the same data, and the amplitude of the output waveform becomes the maximum level. That is, in this case, the waveforms shown in FIG. 4C 1 and 4C are in exactly the same phase, and the output is exactly doubled.

Therefore, in order for the output level to rise rapidly from the 0 level to the maximum level when the performance key is turned on, the data applied to the exclusive OR gates ₆₀ to ₆₅ must be rapidly increased from "16" to "0". It is good if it decreases. In order to shift from the attack state to the decay state, the data applied to the exclusive OR gates ₆₀ to ₆₅ are sequentially increased from "0" to a predetermined value. To further continue to the sustain state, use the exclusive OR gate 6 above.
The data applied to ₀ to ₆₅ are held at the predetermined values. Then, the amplitude level will be constant.
Then, upon detection of the key-off of the performance key, the data applied to the exclusive OR gates ₆₀ to ₆₅ may be gradually increased from the predetermined value to the data "16". And the above exclusive or gates 6 ₀ to 6 ₅
If the data applied to becomes "16", the output level becomes 0 and no musical tone is output.

The above explained the case where ADSR has each envelope state, but the envelope can be controlled in the same way when it has three envelope states such as attack, sustain, and release, such as an organ sound, or when it has other envelope states. .

In the above embodiment, only one sine wave ROM 7 is provided, and by time-division processing using two timings, t ₀ and t ₁ , the sine wave ROM 7 has the same frequency, opposite directions, and the same magnitude. Two phase-shifted waveforms are read out, and two sine wave ROMs are provided, one of which is used to add the data from the accumulator 3 and the output data of the envelope information generation circuit 5. value and the other
If the data obtained by subtracting the output data of the envelope information generation circuit 5 from the data from the accumulator 3 is applied to the ROM, and the resulting data output from both ROMs are added together by an adder and output. , it is possible to read out the above two waveforms without performing time-sharing processing.

In addition, in the above embodiment, the sine wave is divided into 2 ⁶ (=64) sample points and stored, but generally when the sine wave is divided into 2 ⁿ sample points and stored, the sine wave is read from the sine wave ROM 7. The first and second waveforms are sin2πa+b/2 ⁿ ...Equation (5) sin2πa-b/2 ⁿ ...Equation (6), and the composite waveform is 2sinπ/2 ^n-1 a cosπ/2 ⁿ -1b...Equation (7) becomes. Furthermore, exclusive OR gates such as the exclusive OR gates ₆₀ to ₆₅ described above are provided for the A input terminal of the adder 4, and a clock φ is applied to one end of each of the exclusive OR gates 60 to 65.
The accumulator 3 output is applied to the other end, while
If the output of the envelope information generation circuit 5 is directly applied to the B input terminal of the adder 4, the first and second waveforms will be sin2πa+b/2 ⁿ ...Formula (8) sin2πb-a/2 ⁿ ... Equation (9) becomes, and the composite waveform is 2cosπ/2 ^n-1 a sinπ/2 ^n-1 b...Equation (10
) becomes. Therefore, in this case, the envelope control value is 2sinπ/2 ^n-1 b...Equation (11).

Further, in the above embodiment, two sine waves are added to obtain a composite waveform, but a composite waveform may be obtained by subtraction. That is, in that case,
The composite waveform is ±(sin2πa+b/2 ⁿ −sin2πa−b/2 ⁿ )=±2cosπ/2 ⁿ⁻¹ asinπ/2 ⁿ⁻¹ b (12) (same order of decoding, same below). Therefore, the envelope control value in this case is ±2sinπ/2n ^-1 ...Equation (13). Furthermore, in the same manner as above, if the first and second waveforms are set as in equations (8) and (9), the composite waveform is: ±(sin2πa+b/2 ⁿ −sin2πb−a/2 ⁿ )= ±2sinπ /2 ^n-1 acosπ/2 ^n-1 b...Equation (14), and the envelope control value in that case is ±2cosπ/2 ^n-1 b...Equation (15).

Similarly, a composite waveform can be obtained by adding or subtracting two cosine waves. That is,
When the first and second waveforms are cos2πa+b/2 ⁿ ...Equation (16) cos2πa-b/2 ⁿ ...Equation (17), cos2πa+b/2 ⁿ +cos2πa-b/2 ⁿ =2cosπ/2 ^n-1 acosπ /2 ^n-1 b...Formula (18) Or, ±(cos2πa+b/2 ⁿ -cos2πa-b/2 ⁿ ) =±2sinπ/2 ^n-1 asinπ/2 ^n-1 b...Formula (19).

Therefore, in the case of equation (18), the envelope control value is 2cosπ/2 ^n-1 b...Equation (20), and in the case of equation (19), the envelope control value is 〓2sinπ/2 ^n-1 b ...Equation (21) is obtained.

Similarly, if the first and second waveforms are set as cos2πa+b/2 ⁿ ...Equation (22) cos2πb-a/2 ⁿ ...Equation (23), cos2πa+b/2 ⁿ +cos2πb-a/2 ⁿ =2cosπ/2 ^n-1 acosπ/2 ^n-1 b...Equation (24) ±(cos2πa+b/2 ⁿ -cos2πb-a/2 ⁿ ) =〓2sinπ/2 ^n-1 asinπ/2 ^n-1 b...Equation (25) and Become. Therefore, in the case of Equation (24), the envelope control value is 2cosπ/2 ^n-1 b...Equation (26), and in the case of Equation (25), the envelope control value is 〓2sinπ/2 ^n-1 ... Equation (27) is obtained.

In addition, in the above embodiment, the sine wave ROM 7 is configured to store the sine wave waveform over one period. For example, when storing a 1/4 waveform and accessing it, it is necessary to read it back. It is also possible to obtain data for one period of the waveform by performing the following steps or by inverting the sign of the output waveform.

Furthermore, in the above embodiment, a sine wave of the relevant scale frequency, that is, a fundamental wave, is obtained in response to the operation of a performance key, but a case where a higher order sine wave, that is, a harmonic wave is obtained in the same way is the above frequency information conversion
If the output from ROM2 is shifted by a predetermined bit and then supplied to the accumulator 3, a sine wave can be generated.
The waveform read from the ROM 7 is a high-order sine wave. Therefore, it is also possible to obtain the fundamental wave and harmonic waves of a predetermined order using a plurality of independent circuits in the same manner as in the above embodiment, and to synthesize them to obtain the final output. Furthermore, the circuit configuration shown in Fig. 1 above can be configured to perform time-division processing, so that one sine wave ROM 7, adder 4, and other circuits can be used in common to obtain the fundamental wave and harmonics. By finally synthesizing them, one musical tone can be formed.

In addition, although the above embodiment outputs one musical tone for one performance key, in order to output musical tones corresponding to a plurality of performance keys, that is, to enable chord performance, it is necessary to It is also possible to provide a plurality of circuits with the circuit configuration shown in the figure and assign the operated performance keys to each circuit so that musical tones can be output independently. By time-divisionally driving the device, a single sine wave ROM 7, adder 4, and other circuits can be used in common to obtain a plurality of musical tones.

Therefore, one sine wave ROM 7, adder 4,
By sharing other circuits, it is possible to time-divisionally process a plurality of musical tones of different scale frequencies, each musical tone consisting of a fundamental wave and a plurality of overtones.

Furthermore, in the above embodiment, the sine wave ROM 7
When specifying an address, it was done by sequentially stepping at a phase angle corresponding to the scale frequency, but the above sine wave is
Even if the ROM 7 is accessed, a sine waveform having a similar scale frequency can be obtained.

In addition, without departing from the gist of the present invention,
Various modifications and applications are possible.

As described in detail above, the present invention reads a sine wave or cosine wave stored in a waveform memory in advance according to a scale frequency, and uses the sine wave or cosine wave from the waveform memory in an electronic musical instrument that generates musical tones. are read as two waveforms having the same frequency and whose phases are shifted in opposite directions by an amount according to envelope data that changes over time, and by synthesizing these two read waveforms, the above 2. Since the envelope control can be performed on the sine wave or cosine wave according to the phase shift amount of the two waveforms, there is no need for a multiplier for multiplying the wave height value and the envelope control value. This reduces the hardware and is very effective in integrating the circuits of electronic musical instruments.Furthermore, the waveform obtained by combining the two waveforms mentioned above has a phase shift from the original waveform. Therefore, even when envelope control is performed continuously, it has the advantage that the pitch and timbre of the output musical tone are not affected at all.

In addition, if one waveform memory is accessed in a time-sharing manner to obtain the two waveforms mentioned above, the hardware of the waveform memory is halved compared to the case where two waveform memories are provided, and the hardware is further reduced. This has the advantage of reducing the amount of

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a circuit configuration diagram showing the main parts of this embodiment, FIG. 2 is a diagram showing data stored in the sine wave ROM of FIG. 1, and FIG. 1 is a diagram showing the clock pulses for driving the circuit of FIG. 1 and their time-division operation states, and FIGS. 4A to 4C are diagrams showing two waveforms read out in a time-division manner from the waveform memory and the waveforms synthesized. FIG. 3 is a diagram showing a waveform that has been subjected to envelope control. 1... Keyboard, 2... Frequency information conversion
ROM, 3...Accumulator, 4...Adder, 5...Envelope information generation circuit, ₆₀ to ₆₅ ...Exclusive OR gate, 7...Sine wave ROM, 8...Accumulator.

Claims (1)

[Scope of Claims] 1. Envelope data generation means for generating envelope data that changes over time in an electronic musical instrument that generates musical tones by reading out a sine wave or cosine wave stored in a waveform memory in advance according to a scale frequency. and reading means for reading out the sine wave or cosine wave from the waveform memory as two waveforms having the same frequency and whose phases are shifted in opposite directions by an amount according to the envelope data, and this reading means and a synthesizing means for synthesizing the two waveforms read out by the electronic musical instrument, the envelope of the sine wave or cosine wave being controlled based on the amount of phase shift of the two waveforms. control method. 2. The reading means reads, from the waveform memory in which sine waves or cosine waves are stored in advance, the two waveforms having the same frequency and whose phases are shifted in opposite directions by an amount according to the envelope data. 2. The envelope control method for an electronic musical instrument according to claim 1, wherein the envelope control method is read out in parts and supplied to the synthesizing means. 3 The reading means reads the first waveform from the waveform memory as sin2π(a+b/2 ⁿ ) (where 2 ⁿ is the total number of sample points in the waveform memory, a is the number of the sample point to be read, and b is 2 Data indicating the amount of phase shift of two waveforms) is read out, and then sin2π(ab/ ²ⁿ ) or sin2π(ba/2n ⁾ is read out from the waveform memory as the second waveform.
), and the synthesizing means combines the first waveform and the second waveform.
Claims characterized in that a waveform of 2sinπ/2 ^n-1 a cosπ/2 ^n-1 b or 2cosπ/2 ^n-1 a sinπ/2 ^n-1 b is obtained by synthesizing the waveform of An envelope control method for an electronic musical instrument according to item 1 or 2. 4 The reading means reads the first waveform from the waveform memory as sin2π(a+b/2 ⁿ ) (where 2 ⁿ is the total number of sample points in the waveform memory, a is the number of the sample point to be read, and b is 2 Data indicating the amount of phase shift of two waveforms) is read out, and then sin2π(ab/ ²ⁿ ) or sin2π(ba/2n ⁾ is read out from the waveform memory as the second waveform.
), and the synthesizing means combines the first waveform and the second waveform.
2cosπ/2 ^n-1 a sinπ/2 ^n-1 b, -2cosπ/2 ^n-1 a sinπ/2 ^n-1 b, 2sinπ/2 ^n-1 a cosπ/2 ⁿ An envelope control method for an electronic musical instrument according to claim 1 or 2, characterized in that a waveform of ^-1 b or -2 sin π/2 ^n-1 a cos π/2 ^n-1 b is obtained. 5 The reading means reads the first waveform from the waveform memory as cos2π(a+b/2 ⁿ ) (where 2 ⁿ is the total number of sample points in the waveform memory, a is the number of the sample point to be read, and b is 2 data indicating the amount of phase shift of two waveforms), further reads cos2π(a-b/ ²ⁿ ) as a second waveform from the waveform memory, and the synthesizing means combines the first waveform and the second waveform.
The envelope control method for an electronic musical instrument according to claim 1 or 2, characterized in that a waveform of 2cosπ/2 ^n-1 a cosπ/2 ^n-1 b is obtained by synthesizing the waveform of . 6 The reading means reads the first waveform from the waveform memory as cos2π(a+b/2 ⁿ ) (where 2 ⁿ is the total number of sample points in the waveform memory, a is the number of the sample point to be read, and b is 2 data indicating the amount of phase shift of two waveforms), further reads cos2π(a-b/ ²ⁿ ) as a second waveform from the waveform memory, and the synthesizing means combines the first waveform and the second waveform.
A waveform of -2sinπ/2 ^n-1 a sinπ/2 ^n-1 b or 2sinπ/2 ^n-1 a sinπ/2 ^n-1 b is obtained. An envelope control method for an electronic musical instrument according to scope 1 or 2.