I have been using Arrangers from a LONG time ago now, most 61 keys with some exceptions, the Ketron SD1 basically....and now with the Genos...that is 76.
Having said that, I do not know if is because of the smaller footprint in Genos vs T5 76, but, the first week it took some getting used to some controls mostly for the drastic user interface change, that now I love.
I find myself "at home" with the 76 keys, and I do NOT think that I could get back to the 61 keys, I like the re-newly re-discover key range, I no longer have to hurry up to either change the Octave or make a change of registrations with the adjusted octave range....it "flows" more naturally.
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mdorantes