The Six-Trak was a budget offering by Sequential that was one of the earliest multi-timbral midi synths. Multi-timbral in that this 6 voice single oscillator poly can also work as six independant mono-synths. Unison mode makes for great leads and really fat basses, and there is also a Stack mode that allows up to six different voices to be stacked on a single note for nifty effects & Such. Although the mod routings of this synth are pretty basic, there are 3 envelope generators (VCO, VCF & VCA). A single oscillator synth built off of the Bally-Sente Curtis chipset, it works rather nicely as a monosynth with a filter that can range from smooth to very dirty. Its best feature is it's MIDI implementation and its usage of continous controllers for tweaking the parameters.