Abstract: A tone generation control unit has four waveform read/write channels for selectively reading or writing data in a waveform memory. A plurality of waveform signals stored in the waveform memory are converted into analog signals to be subjected to timbre and tone volume control through voltage-controlled filters and voltage-controlled amplifiers before being fed to a mixing adder. An output signal of the mixing adder is converted into a digital signal which is stored in the waveform memory again through processing of the tone generation control unit.

Abstract: A CPU reads out sampled waveform data stored in a waveform memory and detects a peak value of the read-out data for each predetermined block using working registers, thereby obtaining an interpolated envelope curve. The CPU then divides the sampled waveform data by the interpolated envelope curve to obtain a normalized sound waveform without any envelope in an original sound signal.

Abstract: External sound signal coupled through a MIC IN terminal is fed through an operating switch panel section to an A/D converter for conversion to a digital signal. The digital signal is stored in a record memory through a waveform R/W controller under the control of a CPU. The digital signal stored in the record memory is read out from the CPU according to control data stored in a work memory to be fed to an external sound system for sounding.

Abstract: A CPU supplies data write and read commands to only an address control section, and the address control section then designates, for the purpose of writing and reading data, addresses of a waveform memory in which external sound waveform data is stored.

Abstract: Under the presence of an internally generated mandolin clock (MDN) or an externally generated mandolin clock (MDN'), an envelope clock (ENV-CLK) obtained in accordance with a lower bit output having three-bit signals (including the LSB) is supplied through AND gates to an envelope counter. The counter is set in an up count state in response to an output from a flip-flop set in response to a key on pulse. When a carry signal is generated by the envelope counter, the counter is set in a down count state. In the latter case, the fourth-bit signal from the LSB of the output from the binary counter is gated through the AND gate. The envelope counter counts down the envelope clock (ENV-CLK) having a period twice that of the envelope clock (ENV-CLK) in the up count state.

Abstract: A basic coefficient to be used for calculation of a transfer function of a digital filter is read out from a ROM according to a cutoff frequency of a desired filter. The value of the coefficient read out from the ROM is gradually varied according to a desired resonance characteristic by an arithmetic circuit so as to reduce the memory capacity of the ROM for storing coefficients.