I use a Yamaha CS01 Monophonic Analog synthesizer that I play through the S900's Mic/Line in and use the effects and harmonizer to create pseudo polyphonic analog synth voices.
The little CS01, despite its small size and mini keys, is an extremely fat sounding analog synth with an oscillator range down to 32' and features a very nice 12dB resonant VCF filter and wickedly juicy Pulse Width Modulation
I can achieve some really cool sounds and effects by using this relatively obscure combination.
The CS01 is about 27 years old and in mint condition...I also have the breath controller for it which allows for incredible expression.
I believe Chick Corea used to use one, and they are very popular with today's electronic musicians.
Ian
[This message has been edited by ianmcnll (edited 03-25-2009).]
_________________________
Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.