The need for 76-keys is mentioned every time a new arranger is released, but it is not clear why you would want that.
First of all: if you bought an arranger to play piano or organ, you bought the wrong instrument. If you love the Yamaha sound like I do, then you buy a Motif. If you want an orchestra at your fingertips, then you buy an arranger.

I must admit that I sometimes run out of keys on my PSR3000 - mostly this happens around the splitpoint for left and right side of the keyboard. You have about 1.5 octaves for the chords, so there remains 3.5 octaves for melody - 3.5 to 4 octaves is the limit for most wind- and brass instruments anyway.
Even the 1.5 octave for the chords are sometimes not sufficient and - depends what key I am playing in - I have to find other ways to play certain chords if I run out of keys. And then you are left with 3.5 octaves to play around with. True, if you use organ and piano voices it is just not enough, but for most voices it is enough - for some voices it is even too many.

So why not hook up a 76-key controller to your arranger? Maybe Yamaha should give demos where the demonstrators just do that.

What would the advantage be with 76 keys?
Well, with 61 keys I have to search for other ways to play a chord, or I should shift the splitnotes, but then I run out of low notes for my melodies and or improvs. Espescially organs, accordions, pianos and other voices like that, 3.5 octaves is not much. So for those voices you might want an extra octave.
It is not even necessary to go from C to C, on the left side you could start with a F or G and you could end on the right with a F or G as well.


[This message has been edited by drdalet (edited 09-06-2008).]