JPH0311477B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention provides an electronic musical instrument in which a musical sound waveform is formed by individually calculating the waveform amplitude value of each sample point of the musical sound waveform by Fourier synthesis. An electronic musical instrument that effectively temporally changes a musical sound waveform with a small amount of waveform synthesis calculations by performing interpolation calculations on musical sound waveforms calculated and synthesized at discrete temporal representative points at minute time intervals. .

(2) Conventional technology and problems Conventionally, in digital electronic musical instruments,
Many methods have been proposed in which a waveform amplitude value at each sample point of a musical sound waveform is generated by some method, and this is read out at a readout rate corresponding to the pitch frequency. The simplest method is the so-called "waveform memory method" in which the waveform data itself is stored and read out, and a method in which analog input is A/D converted into waveform data also follows this method. However, in order to change the musical sound waveform according to the musical range, an enormous amount of memory is required, and the musical sound waveform does not change over time. In addition, methods have been considered to calculate parameters using various continuous functions, or to calculate temporal changes in musical waveforms in real-time waveform synthesis using frequency modulation methods. The correspondence with the timbre is extremely unnatural to human senses, and it has been difficult to obtain the desired timbre.

On the other hand, the musical waveform generation method using Fourier synthesis has been widely adopted with various improvements to compensate for the drawback that it requires a large amount of waveform synthesis calculations because the harmonic coefficient parameters naturally correspond to auditory timbre evaluation. It's here. In the musical sound waveform generation method using Fourier synthesis, it is the composition ratio of harmonic coefficients that determines the timbre of a musical sound, and in order to change the musical sound waveform over time, multiple memories are used to select many harmonic coefficients. A method was considered to do this, but it had the disadvantage that it was not possible to obtain sufficient timbre change despite the enormous circuit scale. Also, special public service 53-46445
The method of multiplying a set harmonic coefficient by a "formant filter" as described in the issue, and the method of multiplying the set harmonic coefficient by a "formant filter", and the method of multiplying a time-varying function for each harmonic coefficient as described in JP-A-57-172396. All multiplication methods require a harmonic coefficient multiplication circuit, and in order to perform multiplication and accumulation operations in musical waveform calculations, individual temporal changes are calculated over higher-order harmonic coefficients. There are limits to what can be done in terms of circuit scale, amount of calculations, calculation speed, etc., and there is a drawback that it is not sufficient for changing the temporal sound waveform of a digital musical tone.

(3) Structure and Purpose of the Invention The present invention has been made in view of the above-mentioned points, and it is possible to avoid increasing the circuit scale and calculation speed of a musical sound waveform generation circuit that calculates and synthesizes temporally changing musical sound waveforms. The present invention is characterized by comprising an interpolation circuit for obtaining a waveform interpolation value corresponding to a minute time interval, and a storage circuit for storing a target value and a current value for the waveform interpolation.

(4) Embodiments of the invention Hereinafter, embodiments of the invention will be described in detail with reference to the drawings.

FIG. 1 is a conceptual diagram for explaining the configuration of an electronic musical instrument according to the present invention, in which 3 is a key press detection/tone assignment circuit, 4 is a harmonic coefficient circuit, 5 is a waveform generation circuit, and 6 is a waveform memory. circuit, 7 is a pitch frequency circuit,
8 is a D/A conversion circuit, and 9 is an envelope circuit.

That is, in the key press detection/sound generation assignment circuit 3, control signals corresponding to the tone color information and performance information inputted through the keyboard 1 and the tone color setting tablet 2 are supplied to each section. In the harmonic coefficient circuit 4, Fourier harmonic coefficients for musical sound waveform synthesis calculation are set in accordance with the timbre information from the key press detection/tone generation assignment circuit 3. In the waveform generation circuit 5, a musical sound waveform is sequentially calculated and synthesized using the Fourier harmonic coefficients from the harmonic coefficient circuit 4, and is stored in the waveform storage circuit 6.
supply to. On the other hand, in the pitch frequency circuit 7,
Generates a readout signal corresponding to the musical tone frequency based on the performance information from the key press detection/sound generation assignment circuit 3,
A musical sound waveform corresponding to the musical tone frequency is read out from the waveform storage circuit 6. In addition, in the envelope circuit 9, amplitude modulation data such as the rise and fall of individual musical tones and envelope characteristics are set based on the performance information from the key press detection and sound generation assignment circuit 3. (The above operations are performed digitally in time division,
It is possible to save circuit scale. )D/A
In the conversion circuit 8, the musical sound waveform corresponding to the musical tone frequency read out by the pitch frequency circuit 7 from the waveform storage circuit 6 is digital-to-analog converted, multiplied by the amplitude modulation data from the envelope circuit 9, and converted into an analog signal. Get signal output. The analog signal output from the D/A conversion circuit 8 is converted into sound by a sound system 10 including an effect circuit, an amplifier, and a speaker, and is produced as the sound of an electronic musical instrument.

FIG. 2 shows a specific configuration example for explaining the musical sound waveform synthesis calculation processing section according to the present invention, which is provided in the waveform generation circuit 5 shown in FIG. In FIG. 2, 11 is an arithmetic circuit that performs a Fourier synthesis operation, 12 is a sine function generation circuit that generates trigonometric function data for the Fourier synthesis operation, and 13 is an interpolation operation for musical waveform data that is the arithmetic result of the arithmetic circuit 11. 14 is a current value memory circuit in which the musical sound waveform data to be read out represents the current value; 15 is an interpolation based on the musical waveform data of the target value memory circuit 13 and the current value memory circuit 14; A waveform interpolation circuit that obtains the calculated musical tone waveform data, 16 a timing circuit that controls the time division timing within the waveform generation circuit 5 and the operation timing with the entire circuit, and 17 a timing circuit that obtains the output musical tone waveform data of the waveform interpolation circuit 15. A write circuit 18 writes data into the value memory circuit 14, and a read circuit 18 reads out musical waveform data from the current value memory circuit 14 and finally supplies it to the waveform storage circuit 6.

Regarding the specific configuration example shown in FIG. 2, to explain the operation until the musical sound waveform is calculated and synthesized in the waveform generation circuit 5, generally, in the waveform generation circuit 5, F(s)= _N 〓 ⁿ⁼¹ Cn・sin (2πns/S)...The amplitude values of the musical sound waveform are sequentially calculated by equation (1). where n is the harmonic order, N is the highest harmonic order,
s is the sample point, S is the number of samples in one period, Cn
is a harmonic coefficient set by the harmonic coefficient circuit 4. Although equation (1) is sufficient when synthesizing a tone with a constant musical sound waveform, when synthesizing a musical sound waveform that changes over time, a temporal parameter t is used in addition to this sampling constant s. F(s, t) = _N 〓 ⁿ⁼¹ Cn(t)・sin(2πns/S)...It is necessary to perform calculation according to equation (2). This calculation is essentially asynchronous and is necessary every time the calculation parameters s and t change, so the number of overtones may be limited to a small number due to the limits of circuit scale and operating speed, or the precision of the sampling point for one cycle may be limited. I had to limit it.

In the specific configuration example shown in FIG. 2 for explaining the musical sound waveform synthesis calculation processing part according to the present invention, the musical sound waveform synthesis calculation as described above is executed only at a plurality of temporal representative points, and the interpolation circuit 15
By obtaining interpolated values of multiple waveforms corresponding to points on the time axis that are smaller than the multiple temporal representative points, the time of the musical waveform can be effectively calculated with a small amount of waveform synthesis calculations as a whole. Achieve positive change. This operation will be explained using the waveform diagram shown in Fig. 4.
FIG. 4a shows a conventional waveform interpolation method, in which a value Q obtained by linearly interpolating sample value P1 at time T1 and sample value P2 at time T2, and further a value R.
1, the value R2,... Although this waveform interpolation method is effective for compensating for the roughness of sample points in waveform data, very high-speed interpolation calculations are required to follow temporal changes in musical waveforms in real time. , low-order interpolation is often used as a sampling noise removal method.
FIG. 4b shows the operation of the interpolation circuit 15 according to the present invention, in which the current tone waveform L1 and the tone waveform L2 at a certain point in time representative of temporal changes correspond to the same sample time T3. Obtain sample values S1 and S2, and use these sample values S1 and S
The value R1, or the value R2, or the value R3, etc. is determined as the interpolation value of 2. This fourth
The difference between the waveform interpolation methods in Figure a and Figure 4B is as follows:
While the former interpolates between two points of one type of waveform at a high speed according to the sampling speed as interpolation on the time axis, the latter according to the present invention is so-called interpolation of sample values of two types of waveforms, and This allows the musical tone waveform L2 at a certain point in time, which is representative of a physical change, to be set at a slow speed of several hundred times the sampling interval, which is very effective for realizing temporal changes in musical tone waveforms with high precision.

In FIG. 2, the arithmetic circuit 11 performs Fourier waveform synthesis calculation at time t according to equation (2). For example, when a harmonic coefficient as shown in FIG. 5a is given from the harmonic coefficient circuit 4, a waveform signal F1(x) as shown in FIG. is obtained and transferred to the target value memory circuit 13. Next, after a certain period of time corresponding to the temporal change of the musical sound waveform, when a harmonic coefficient as shown in FIG. 6a is given from the harmonic coefficient circuit 4 under the control of the timing circuit 16, From this, a waveform signal F2(x) as shown in FIG. 6b is obtained and transferred to the target value memory circuit 13 again. In the interpolation circuit 15,
An interpolation operation is performed to obtain an interpolated value between the tone waveform data in the current value memory circuit 14 and the tone waveform data in the target value memory circuit 14, and the operation result is stored again as tone waveform data in the current value memory circuit 14. This operation will be explained using the waveform diagram shown in FIG. 7. In general, in order to interpolate at equal intervals between waveform A and waveform E in FIG. 7a as waveform B, waveform C, and waveform D, Two types of memory circuits are required, each corresponding to the musical waveform data of waveform A and the musical waveform data of waveform E in FIG. A third memory circuit for storing musical waveform data is also required. However, in the interpolation circuit 15 in FIG. 2, when the waveform A in FIG. 7b is used as musical waveform data in the current value memory circuit 14, and the waveform G in FIG. ,1
The result of the interpolation operation for the second time is waveform B in FIG. 7b, and this is stored again as a musical waveform in the current value memory circuit 14, so that the interpolation operation is performed by two types of memory circuits. In the second interpolation calculation, waveform B in FIG. 7b is used as musical waveform data in the current value memory circuit 14, and waveform G in FIG. 7b is used as musical waveform data in the target value memory circuit 13. The interpolation result becomes a waveform C shown in FIG. 7b, which is again stored as a musical tone waveform in the current value memory circuit 14. Expressing the above interpolation calculation according to equation (2), the musical waveform data of the target value memory circuit 13 that is calculated and synthesized at regular intervals is F1 (s, t1) = _N 〓 ⁿ⁼¹ Cn (t1)・sin(2πns/S)...Equation (3) is obtained, and the musical waveform data of the current value memory circuit 14 is F2(s, t) = _N 〓 ⁿ⁼¹ Cn(t)・sin(2πns/S)... It can be expressed as equation (4). For example, if we set a constant asymptotic parameter: M and express the interpolation result: IP (s, t), then IP (s, t) = F2 (s, t) + M・(F1 (s, t1) -F2 (s, t))...Equation (5) is obtained. This is F2 (s, t′) in the next interpolation operation
Therefore, the overall recurrence formula representing the waveform interpolation calculation is: (F1 (s, t1) - F2 (s, t, k+1)) = M・(F1 (s ,t1)−F2(s,t,k))
…(6), and the constant asymptotic parameter: M is O<M<1 …The general solution when formula (7) is IP(s, t, k) = (F1(s, t1) ・( 1−M ^n-1 ) +IP(s, t, 1)・M ^n-1 ...Equation (8) is obtained, and asymptotic interpolation is performed exponentially as shown in Figure 7b. As a condition, if the asymptotic parameter M is, for example, M = 0.5 (or the nth root of 2), then the interpolation circuit 15 in Fig. 2 can be specially simplified using a binary shift circuit and a simple addition circuit. On the other hand, as the number of interpolation points increases, the interpolation calculation result becomes
Waveforms D, E, F, etc. in Figure b are obtained, and it can be seen that the waveforms change more smoothly. Also, focusing on the calculation speed, the musical waveform data changes during the operation of the calculation circuit 11 at a relatively long time interval every time the Fourier waveform synthesis calculation is completed according to equation (2). Considering the human perceptual discrimination ability, a sufficient calculation time of 2 to 3 msec can be assumed. On the other hand, in equation (2), when changing the harmonic coefficient Cn(t) in real time and supplying it from the harmonic coefficient circuit 4, the calculation time of the waveform generation circuit 5 is several μsec even if the number of sample points is limited.
This difference in speed has a very serious effect when actually configuring a circuit.

FIG. 3 shows another specific configuration example for explaining the musical sound waveform synthesis calculation processing section according to the present invention, which is provided in the waveform generation circuit 5 shown in FIG. In FIG. 3, 5 is a waveform generation/waveform interpolation circuit as shown in FIG. 2, 21 is an interpolation value memory circuit that temporarily stores the output musical waveform data from the waveform generation/waveform interpolation circuit 5, and 22 is an interpolation Value memory circuit 21
23 is a time setting circuit that controls the operation timing of the waveform generation/waveform interpolation circuit 5 and the temporal interpolation circuit 22. That is, after performing the above-mentioned waveform interpolation calculation as shown in FIG.
It performs conventional temporal interpolation calculations as shown in Figure a. To explain this operation following equation (8), the musical waveform data transferred to the interpolation value memory circuit 21 is an interpolation value transferred from the waveform interpolation circuit 15 to the current value memory circuit 14 every moment, and the parameter: s , t, k, j, IP(s, j, t, k) is expressed as in equation (9). Here, s is the sample point of the waveform synthesis calculation, j is the temporal interpolation parameter in the temporal interpolation circuit 22, t is a plurality of temporal representative points for musical waveform synthesis, and k is the waveform in the waveform generation/waveform interpolation circuit 5. It is an interpolation parameter. The temporal interpolation circuit 22 performs an interpolation operation on the sample point s.

IP(s,j,t,k) =IP(s,1,t,k) +Q(j)・(IP(s+1,1,t,k) -IP(s,1,t,k))... Obtain the temporal interpolation value of equation (10). Here, Q(j) is an interpolation function that determines the interpolation characteristics, and in the case of linear interpolation as shown in Figure 4 a, it is realized by a linear function, and in the case of exponential interpolation, it is realized as described above. This is realized by a shift circuit or the like. In the specific configuration example shown in Figure 3, the overall circuit configuration is relatively large, but when considered as the overall operation of musical sound waveform synthesis calculation, it is possible to save sample points and create waveforms that correspond to temporal changes in musical sound waveforms. In terms of margin for synthesis calculation interval,
This method enables the execution of a computational amount that was impossible to achieve with conventional electronic musical instruments, and it functions effectively depending on the parameter settings.

(5) Effects of the Invention As explained above, according to the present invention, an electronic musical instrument that forms a musical sound waveform by Fourier synthesis calculation requires a high-speed circuit configuration for calculating temporal changes in a musical sound waveform. The musical sound waveforms that are calculated and synthesized at low speed are interpolated and calculated at minute time intervals using a feedback storage circuit and an interpolation circuit, and the musical waveforms are effectively changed over time with a small amount of waveform synthesis calculations. By realizing such a musical waveform generation method, it is possible to easily provide an electronic musical instrument with rich musical tones, and it will greatly contribute to the creation of high-quality music.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram for explaining the configuration of an electronic musical instrument according to the present invention, and FIG. 2 shows a musical sound waveform synthesis calculation processing section according to the present invention provided in the waveform generation circuit 5 shown in FIG. A specific configuration example for explanation, FIG. 3, shows the waveform generation circuit 5 shown in FIG. 1.
A specific configuration example for explaining another embodiment of the musical sound waveform synthesis arithmetic processing section according to the present invention provided in FIG. 5 and 6 are waveform diagrams for further explaining the operation of the specific configuration example shown in FIG. 2, and FIG. 7 is a waveform diagram for explaining the operation of the specific configuration example shown in FIG. 2. It is a waveform diagram for further explanation. In the figure, 1 is a keyboard, 2 is a tone setting tablet, 3 is a key press detection/tone assignment circuit, 4 is a harmonic coefficient circuit, 5 is a waveform generation circuit, 6 is a waveform storage circuit, 7 is a pitch frequency circuit, 8 is a D/A conversion circuit;
9 is an envelope circuit, 10 is a sound system, 11 is an arithmetic circuit, 12 is a sine function generation circuit, 13 is a first memory circuit, 14 is a second memory circuit, 15 is an interpolation circuit, 16 is a timing circuit, 21 is a An interpolation value memory circuit, 22 a temporal interpolation circuit, and 23 a time setting circuit.

Claims (1)

[Scope of Claims] 1. In an electronic musical instrument in which a musical sound waveform is formed by individually calculating the waveform amplitude value of each sample point of a musical sound waveform by Fourier synthesis, a temporally changing musical sound waveform is Calculation and calculation at time representative points
a musical sound waveform generation circuit for synthesizing, a target value storage circuit for temporarily storing the musical sound waveform calculated and synthesized in the musical sound waveform generating circuit as a target value, and a current value storage circuit for storing the current musical sound waveform as a current value. , an asymptotic parameter setting circuit for setting asymptotic parameters for the two types of musical sound waveforms read out from the target value storage circuit and the current value storage circuit; a waveform interpolation calculation circuit that calculates an interpolated value of the two types of musical waveform data corresponding to a point on a time axis that is smaller than the plurality of temporal representative points from the two types of musical waveform data and the asymptotic parameter; and a waveform writing circuit that writes the output waveform of the waveform interpolation calculation circuit into the current value storage circuit as a current value for the next calculation, and a waveform readout circuit that reads out the musical waveform output from the current value storage circuit. , an electronic musical instrument characterized in that a musical sound waveform can be effectively temporally changed with a small amount of waveform synthesis calculations. 2. The electronic musical instrument according to claim 1, further comprising: a difference value setting circuit for determining a difference value between the two types of musical waveform data read out from the target value storage circuit and the current value storage circuit; The circuit includes an increment value setting circuit that binary-shifts the difference value to obtain increment value data, and an interpolation arithmetic circuit that calculates an interpolated value from the two types of musical waveform data and the increment value data. An electronic musical instrument characterized by having functional asymptotic characteristics. 3. In an electronic musical instrument in which a musical sound waveform is formed by individually calculating the waveform amplitude value of each sample point of a musical sound waveform by Fourier synthesis, a temporally changing musical sound waveform is calculated at a plurality of temporally representative points.・
a musical sound waveform generation circuit for synthesizing, a target value storage circuit for temporarily storing the musical sound waveform calculated and synthesized in the musical sound waveform generating circuit as a target value, and a current value storage circuit for storing the current musical sound waveform as a current value. , an asymptotic parameter setting circuit for setting asymptotic parameters for the two types of musical sound waveforms read out from the target value storage circuit and the current value storage circuit; a waveform interpolation calculation circuit that calculates an interpolated value of the two types of musical waveform data corresponding to a point on a time axis that is smaller than the plurality of temporal representative points from the two types of musical waveform data and the asymptotic parameter; a waveform writing circuit that writes the output waveform of the waveform interpolation calculation circuit into the current value storage circuit as a current value for the next calculation; and a waveform writing circuit that stores the output data of the waveform interpolation calculation circuit for two consecutive sample points. first and second sample value storage circuits; and a temporal interpolation circuit that calculates interpolated values of a plurality of waveforms corresponding to finer temporal sample points from the output signals of the first and second sample value storage circuits. and an interpolation waveform readout circuit that reads out a musical sound waveform output from the temporal interpolation circuit, and is configured to effectively temporally change a musical sound waveform with a small amount of waveform synthesis calculations. 4. The electronic musical instrument according to claim 3, further comprising: a difference value setting circuit for determining a difference value between the two types of musical waveform data read from the target value storage circuit and the current value storage circuit; The circuit includes an increment value setting circuit that binary-shifts the difference value to obtain increment value data, and an interpolation arithmetic circuit that calculates an interpolated value from the two types of musical waveform data and the increment value data. An electronic musical instrument characterized by having functional asymptotic characteristics.