When I begin to try to learn a piece, the first step is to figure out which key it’s in.
It’s largely due (in my opinion) to my lever harp: Its range is kind of small (at least for modern instruments, I’ve found).
A “standard tuning” for the lever harp (in Irish Music, anyway) is that of E♭ Major, with all levers down. This lets You use the modes in this table.
A♭, D♭, F♯ and B Major are all beyond my reach with this tuning (along with many of the minor scales). I get around songs modulating by a flip of a lever, or a modal arrangement of my levers. It’s not hard, but when compared to something like guitar it is not just a change of frets or strings.
This limitation makes me think a lot about the underlying harmonies of any piece I play. And I would say that it has forced me to become more versed in modal theory than I would have been.
It also bettered my arrangment skills, which I use every day to learn pieces. So I am very thankful that it’s so.