Sequential Circuits SCI Six Trak c 1985

via this auction

Note the listing states this was essentially a Prophet-600 with multitrack controls and it has SSM filters. That is not correct. It has the same synth engine as the Multi-Trak and it uses CEM filters. The Prophet-600 also had CEM filters. The only Sequential Circuits synth to have SSM filters was the Prophet-5 Rev 1 & 2. You can see a listing of what synths used what chips on Wikipedia here.