PS, Hardi plays lead on his 5-string; he just is able to play things other than usual D, G, and A-key fiddle tunes as lead. Should be true of viola as well given the stringing/tuning similarity. Music not written originally for fiddle or whistle. Or take any fiddle tune's MIDI and use a notation program to move it into a key that fits the viola, and go for it. Chorded instruements can easily back YOU up in C, F, etc.

~Susan