An electronic musical instrument which has a keyboard and creates a musical tone by striking keys of the keyboard, is provided with an operation control circuit and an adder both for effecting keyboard switch chattering prevent operation processing and touch response select operation processing, a timing control circuit for controlling the switching between the chattering preventing operation and the touch response detecting operation and the scanning of the keyboard switches to detect their status, a musical tone generator for performing a musical tone generating operation asynchronously with the keyboard switch scanning operation, the keyboard switch chattering preventing operation and the touch response detecting operation, and a transfer circuit for transferring touch response information to the musical tone generator. High-speed touch response detecting operation processing and chattering preventing operation processing which are difficult to execute by a CPU are carried out by the operation control circuit and the adder on a time-shared basis, and data is properly transferred to the musical tone generator which performs the musical signal generating operation asynchronously with the abovesaid operations, thereby implementing low cost touch response processing which is free from hardware limitations on the number of tones to be simultaneously produced and the generator assignment system. Furthermore, data for internal processing is set for two words on a time-shared basis, and touch response data which has such a natural temporal variation curve as is obtainable with a time constant circuit system is directly operated by the operation control circuit and the adder is then rendered to one-word external output data of high precision and resolution, thereby effectively reflecting the tough response data in musical parameters of musical tones to be created.

A tone generator includes a plurality of tone generation channels each comprising one or more operation channels. One operation channel performs basic operation of a tone signal computing operation (e.g., FM or AM) and a tone signal is generated by using one or more operation channels for one tone generation channel. Tone generation channels in the tone generator are established according to a selected performance mode. In a first mode, the operation channels are divided into N groups and N tone generation channels are established in correspondence to the respective operation channel groups. In a second mode, the operation channels are divided into M groups and M tone generation channels are established in correspondence to the respective operation channel groups wherein N is a different number from M. Tone generation channels of the number required according to the selected performance mode can be established by efficiently utilizing the operation channels of a limited number.

An audio interface is coupled to received a music signal and a microphone signal. The music signal and a volume control signal are combined in a multiplier to produce a volume adjusted music signal. In response to an input signal from a user, the volume control signal is gradually changed in predetermined increment levels. Thus, the multiplier gradually changes the audible volume in these predetermined increment levels. The resulting music and microphone signal are stored in corresponding partitions of a single memory, and thereafter provided to a mixing circuit. The mixing circuit combines signal samples read from the memory to produce four output signals each containing first and second channel samples. The resultant 8 channel samples are gated in a formatter with respective channel mute signals which, when asserted, effectively mute their corresponding channel sample.

An electronic musical instrument is of a type wherein musical tone waveforms are stored in a memory as their sampled amplitudes and sequentially and repetitively read out to constitute tone waveforms. A key depression brings forth frequency information in a digital representation. The frequency information is accumulated to make an address signal for reading out the waveform memory. When a depressed key is moved laterally, a touch detection circuit produces an analog detection signal representing the amount of displacement of the key. In the meanwhile, a clock pulse is counted by an up-down counter and the counting output is converted by a D-A converter to an analog signal to obtain a triangular wave function signal. When the analog detection signal coincides, in amplitude, with the triangular wave function signal, the digital signal from the up-down counter is sampled and held by a sample and hold circuit. Thus a digital signal representing the key displacement is obtained. This digital signal is multiplied with a frequency information in a multiplier and, accordingly, the musical tone frequency is modulated in response to the lateral movement of the key. Thus, the touch vibrato effect is obtained.

An envelope waveform generating apparatus comprising a key code generating device composed of a means for releasing key code data and a means for outputting first and second control signals, a key assignor composed of a means for outputting a third control signal, a level setting means, and a function generator. The envelope waveform generating circuit is provided with a touch response so that the level of envelope waveform may readily be set.