Somehow this thread turned from "How many keys" discussion to "Why Yamaha don't produce 76 keys arranger" war. I don't want to turn some more oil to the fire but I'm not convinced that either of the "two sides" involved here are right.

Arguments of both sides could prove to be right or wrong, depending from what point of view are taken. But arranger manufacturers often behave in a way that's hard to understand for some group (or majority) of the arranger users.

Roland, for instance, produce arrangers without sampler, therefore customers from Eastern Europe, who mostly perform music with specific instruments, prefere Korg (Pa80, Pa1x/pro, Pa800, Pa2x) or Yamaha (PSR9000Pro, Tyros 1/2).

In the upper case, one could also conclude that arranger-with-sampler (or 76-keys-arranger in "our" case) market is too small, and Roland (Yamaha) refuse to make such "non-profitable" product.

IMHO If someone is selling some product for quite long time, there is market for it, and it's profitable. Therefore if someone claims Yamaha doesn't produce 76-keys arranger because it's not profitable (or because they wait to see how the market would respond, and it lasts for decades) he is definitely wrong.

Why the Yamaha behaves in such manner, we can only guess, but will not know, for the same reason we don't know why Roland kicked out chor sequencer. ;-)