Diki:
Looking at the manual the editable midi templates on the S900 are almost identical to Ty2 meaning a controller keyboard can be set up to work- even if not immediately by default as you can on Ty2 (I'm not sure, S900 does not have a 2nd (midiB) port) then by selection and/or editing.

With regard to what can further be done via midi:
If I drive my Ty2 in Keyboard mode with a single "pair of hands" midi track I can try out different style and voice arrangements, tempos, pitch bend etc. etc. as "it" plays the song.
If I record the sysex as I change style variations/fills/endings then feed it back in the next time at playback, whatever style is loaded on the keyboard responds. You sometimes get unexpected effects using sysex so debugging (of the setup used, not the keyboard!)would be necessary to get it reliable but it shows feasibility.

John

[This message has been edited by jwyvern (edited 09-08-2008).]