Mozart played a variety of keyboards. Harpsichord, clavichord, pipe organs and early forte-pianos. None of which had ANY standardized key width... Didn't seem to faze him

The only thing that really got to me was playing a piano accordion with 'lady's keys' which are considerably thinner than even a regular accordion, which is itself a lot less wide than a piano's keys. I could easily span an octave and a fifth (C1-G2:wow: ) on that thing, and it seriously threw off my chops! Regular piano accordion, no sweat, but this thing was just SO small...