When I gig with the PSR-S900, I am always in accompaniment mode and using styles...61 keys are plenty.

I stopped doing solo piano gigs(no vocals) several years ago, and now focus/specialize strictly on solo arranger(again, no vocals).

I don't use SMF, but if I did, 61 keys would also be fine for me.

If you need/want to play left hand bass, you may want more keys...I prefer the freedom of not having to play LH bass, so again, 61 keys are plenty.

I also prefer the PSR's light action...it maybe a sin to some, but it is me I am trying to please, not them.

Ian