The Six-Trak is a 6-voice, polyphonic, multitimbral, programmable analog synthesizer with MIDI, a sequencer, an arpeggiator, and a 4-octave, 49-note (C-C) keyboard. It was one of the first multitimbral MIDI instruments designed to be used with a computer. Software was available for the Commodore 64 computer, then a very popular home personal computer. The software allowed you to program the voices and the sequencer. Sequential marketed the Six-Trak and its software with their Drumtraks drum machine as a complete MIDI system.
The Six-Trak was also designed as a MIDI instrument. Some say that the SixTrak was the first multitimbral MIDI synth to respond to multiple MIDI channels. Each voice can be programmed to any of 100 internal patches and played (via an external sequencer or external keyboard controller) as a separate monophonic synth. Also available was a built-in 800 note sequencer consisting of two multitimbral Six-Trak sequences with individual volume controls. It is also syncable to an external source. To be honest I can't be bothered to set up the midi on it.
Each voice consists of a single Curtis 3394 chip, which basically contains the entire synth engine (one VCO, a VCF, a VCA, and an LFO) except for the ADSR envelope generators. The VCO has coarse and fine tuning, glide (portamento), and available sawtooth, triangle, and pulse (with pulse width modulation) waveforms. Each oscillator can be mixed with the noise generator. The filter section features controls for the cut-off frequency, and resonance. Keyfollow modulation can be set to off, half, or full keyboard. The filter is self-resonating and can be modulated by the oscillator. In each voice the VCO, VCF, and VCA have their own ADSR envelope generators with variable envelope amounts. Both the VCF's and the VCO's ADSRs can be inverted. The LFO can be routed to the VCO, the VCR, and pulse width modulation. Available waveforms for the LFO are square and triangle with controls for amount and frequency. Without a computer, programming is a bit of a chore. The Six-Trak uses parameter access programming via a single data knob and a single two-digit LED display. I have had to repair one of the rubber contact switches as it had split away from it's base.
The Six-Trak features polyphonic portamento (in polyphonic mode), unison mode, and "stack" mode. Stack mode allows each voice to be set to a different patch and played as one complex monophonic sound. Both mono and stack modes are selectable between single and multiple triggering modes. The arpeggiator can be switched to up, down, or assignable, which arpeggiates notes in the order they were played. It can be set to play on voice six as a chord is played with the other five voices.
keyboard can be split into three areas. The pitch wheel is fixed at a
range of a major 3rd up and a minor 3rd down. The modulation wheel controls
the LFO amount. The Six-Trak's patches and Sequences can only be backed
up through MIDI. Also on the back panel is the MIDI interface (IN\OUT),
a stereo audio out jack which doubles as a headphone jack, and a footswitch
(sustain) jack. The Six-Trak's over all dimensions are 28" x 12"
x 4 1/2".