Multi-Trak

The velocity-sensitive, multi—timbral MULTI~TRAK combines the
superior expressiveness of velocity touch sensitivity with the
compositional flexibility o! multi-timbral sound, as pioneered by
Sequential with the Six-Trak and MAX synthesizers. Other features of the MULTl-TRAK include a built-in multi-track sequencer, a chorus effect for richer sounds, a split keyboard, individual audio outputs for each voice, a cassette interface for program and sequence storage, and, of course, MlDI (Musical Instrument Digital Interface).
The block diagram shows the main sub-sections: keyboard,
sequencer, sound memory, voices, and MIDI. Using this as a basis for discussion, we trace backwards from the audio output, to see how the sub-sections work together. There are two types of audio outputs, the Mix outputs and the Track outputs. The Mix outputs, A and B, provide a pseudo-stereo effect from the chorus. Stereo headphones can be plugged into either Mix output. The Track outputs are useful in studio situations, where each voice can be run through its own channel of the main mixer board. If a Track output is used, its voice is removed from the MULTl-TRAK's Mix outputs.
These audio outputs come from the six independent synthesizer
voices. In contrast to homophonic synthesizers, which program each voice with the same sound, each of the MULTI-TRAK's voices can have a different sound (multi-timbre). Each voice has a multi- waveform oscillator (or noises as the principal sound source. The oscillator drives a resonant low-pass filter which contours the timbre, and an amplifier which contours the dynamics. There are three attack—decay-sustain-release (ADSR) envelope generators: one for oscillator frequency, one for filter cutoff frequency, and one for amplifier gain. (The polarity of the first two can be inverted.) A triangle- or square-wave low frequency oscillator (LFO) can modulate oscillator frequency, pulse width, or filter frequency. The amount of LFO modulation can be controlled with the Mod wheel. A second modulation route runs from the oscillator triangle output to the filter frequency, for frequency modulation (FM). Frequency glide ("portamento") and voice volume are programmable. A Pitch wheel is provided for bending notes. Non—programmable master volume and tuning controls are provided. The TUNE switch has been eliminated
by fully-automatic oscillator tuning, although a manual tune
command is still available.