Vortex Sound Research

Hey everyone. I have a very Nooby question… can’t seem to resolve it myself. How does connecting an external sequencer to a production synth actually work??? In this instance, it would involve the Pro2 and the Synthstrom deluge. The Pro2 obviously has CV ins/outs, but I’m still confused about whether an external sequencer would go in via audio, MIDI or CV?!

If somebody with a spare minute knows how to both connect and use this setup, I would be grateful for a response.

Thanks!