Besides the RYTM and A4 (which are both very good friends with my OT), I have the OT drive a Modor NF-1 and a Hypersynth Xenophone. The Xenophone is definitely a bit more compact that the very spacious NF-1 front panel, but they both sound great and integrate well. NF-1 is a digital synth with 7-stage envelopes, plenty of modulation options and a formant filter. The Xenophone is an analog mono with a fantastic filter and lots of modulation as well. Screen is real nice and it's super quick to program. Actually, both of these synths are very quick, workflow-wise. They both compliment my modular system and really tie everything together nicely. But yeah, the OT drives them both.