Note / Octave Select GUI assistant

[bazz1tv]

requested by @RowanDDR

When the user double clicks on a note entry in the pattern editor, a piano pops up that helps you visually select the note and octave you want. This piano should or course be limited in range to the snes.

At, the moment, the base note is c-4, highest is c-6, lowest is IIRC c--2 (negative 2) but notes that low aren't well heard, so there is a current 'practical lower bound' of c-0.

The piano should have those lowest octaves printed but greyed out to indicate potential usability in the future.

Keys should highlight themselves on mouse over. They should if possible also cleanly print octave and/or note-name.

[RowanDDR]

Something like this would be fab (my design):