The SQ1 doesn't drive the Werkstatt in an ideal way (the envelope is not triggered, so the sound is completely on or completely off).
The Volca Keys has a sequencer built in, although it is not a step sequencer like the SQ-1. The SQ-1 could drive a Volca via MIDI.
Moog stuff: Slim Phatty, Minitaur, Werkstatt x2, MF-103, MF-104M, MF Chorus
Running Moog software on Win7 64-bit
Dreams of a Voyager XL some day...