Fiddle, because it would take a lot more time than I've got to get to even a reasonable standard, let alone anywhere near the numerous excellent players who surround me.

Guitar: I tried. I couldn't. I don't really know why - I can do the left hand and pick out tunes OK, but beyond that I just don't know what to do with it.

Cello, not nearly portable enough.

Hurdy-gurdy, because I can't afford one.