It fits easily on a 41 note keyboard in the key that the original 'official' sheet music was in - D. On one of my smaller P/As it can fit on a smaller Kb, but only if I transpose to G. Incidentally, some Kbs are 'pitched' differently - not all run from same start note to same finish note, even if they have the same number of keys - there are very good musical reasons for this. If you have less than 2 octaves, it won't fit, unless you can 'octave jump' somewhere in it.

For non-Kb instruments, much the same applies, except if they are diatonic - you will have to ensure that you can play it in one of the 'native' keys, just trying to squeeze the top and bottom notes into the physical range won't work.