61 v 76.

I examined some of my favorite songbooks and found that some of the piano parts cannot be played as written on a 61-note keyboard, but (almost?) all could be played on a 76-note keyboard. Songs with a range of greater than 5 octaves are not uncommon. But, ever for piano parts with ranges of five octaves or less, a keyboard with more than five octaves may be required. For example, a piano part to have a range that includes "B" below the bass clef and "D" above the treble clef; this range is less than five octaves, but cannot be played on a C-C 61-note keyboard without transposition.

While I am at it, let me say that the Nord Electro 72 form factor is really attractive. 22 lbs, 6 octaves (73-note), compact. I am not going to get one because it is missing other features I want, but the size and weight are great.