Sequential Circuits Six-Trak

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"Sequential Circuits SixTrak
The six-trak is a six voice, multi-timbred unit that features an 800 note sequencer, arpegiator, and 100 patch locations. The back panel features and a single audio out, midi in and out ports, and a control foot switch which can be used to scroll through programs and advance the arpegiator one step at a time.

Multi-Tambral/Keybord modes/Sequencer/Apregiator
The unit can be used in number of keyboard modes which will alter how the voices are assigned. When powered up, the unit is a six voice, homophonic synthesizer. You can program the patch to operate in unison mode which will play all six voice at once (lowest note priority), or normal which assigns one voice to each key press. Triggering may be single or multiple. What is amazing is something SCI calls stack mode, which allows you to assign six separate patches (SIX separate timbres) to one key. When in stack mode you can turn off voices by simply setting their the ‘trak’ volume to zero for the particular voice. The unit can remember two of these stacks in the units memory. Additionally using its internal sequencer, you can assign six separate monophonic voices to each of the one six sequencer tracks. And you can play along with the sequencer using as many of the remaining voices that aren’t being used by the sequence. Once a sequence is recorded you can go back and change the applicable sequence’s patch and volume.

The unit offers a simple arpegiator which uses the sixth voice. It can be assigned to play in an up/down mode or in the order the notes are played. The arepgiator may be latched and the remaining five voices may be used to play on top of the arpegiator. Unfortunately to get the unit to realize you want to change the arpegiation you have to take it out of the latch mode.

The six track has an 800 note sequencer that is divided into two banks. Its a bit on the slim slide and I really don’t use it much. Once a sequence is recorded you can speed up or slow down the sequence from its initial recording speed. You can change the patch it will use to play the sequence but you can insert patch changes in the middle of the sequence. By turning the sequencer’s speed knob all the way to the left, the sequencer will sync to incoming midi clock.


The Voice
Each voice is contained on a single CEM 3394 chip which includes a single VCO, VCA, and VCF. The LFO and three envelopes per voice are software generated. The VCO offers saw, triange, vairable pulse width waveforms, and more than one waveform may be selected at a time. The pulse width may be controlled by the LFO. The VCO may be modulated by its own dedicated ADSR which may be inverted and portmento (glide) is included at the patch level (much better than global i.e. Roland JX8P). The LFO offers either a square or triangle waveforms and can modulate the filter, VCA, and the pulse width. However the amount applied to each of these destinations is set using one LFO parameter and you can only choice if you want this amount to affect each of the three destination. There is no delay for the LFO either. The filter is great it can sound real dirty or pretty clean. The filter offers the cutoff, resonance (self oscillating), three levels of keyboard tracking (on, half, off), LFO on/off, and a dedicated ADSR which may be inverted. Additionally the filter may modulated by the oscillator’s triangle wave which is excellent and offers some really cool sounding effects. Last but not least the filter offers a mixer to mix the level of the oscillator and a dedicated noise source. The VCA has its owned dedicated ADSR and the VCA output level is programmable. Included at the patch level is a parameter to select normal or unison mode (see above).

MIDI
The unit may operate in onmi, poly, or mono mode. In mono mode each monophonic voice is assigned a midi channel so the unit can be used in a multi-tambral fashion via a midi. It would have been nice if the unit used a voice allocation scheme (preferably dynamic allocation scheme) so you could have played more than one voice on each channel if there were unused voices.-but I dont think any manufacturer had implemented this feature back in 1984. The unit can perform system exclusive dumps of its sequences, stacks, 100 programs, or single programs. The unit will send and receive program changes, pitch and modulation wheel movements. Additionally the unit will respond to parameter changes but not send them. (Does anyone know if the ability to send them was implemented on later operating systems). Local on/off is also provided which allows you to turn off the six trak’s keyboard. The best midi feature of the six track is that each parameter will respond to a specific midi continious controller number (cc#). Paramter 0 will respond to message sent by cc #2, parameter 1 will respond to messages sent by cc#3 and so. Essentially, just add 2 to the parameter # and you have identified the CC# that affects the parameter."


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