A very underrated analog synthesizer, in fact the last analog synth Yamaha made. It is a strap-on synth, so it is very easy to use as a synth bass or a lead synth. The most drawback are the mini-keys, but the sound is good. It has a VCF with low-pass only, but it has a resonance slider instead of the earlier model CS01 without the II which had only a switch.All pots are sliders, so it's very easy to see the configuration of the sound and easy to alter the sound. The CS01 II is of course incapable of playing any chords, but it's the same thing with e.g. violin, trumpet, saxophone etc... :-) It looks like a toy, but sounds like an analog synthesizer!
Comments About the Sounds:
Nice analog sound, good for synth bass and leads. (no other use for a mono synth)
(Thanks to Ari Tamminen for this info.)
and Timo Rotonen for the pic