Lots of really good info in this thread!

I find it much easier to stick to a rhythm and change chords correctly when there's a bass player who keeps good time and walks to the next chord.

I know the essential theory behind how trad tunes are, for the most part, constructed, but sometimes the changes don't come when I expect, and that little "boomp boomp boomp" walking bass line gets me to the right chord at the right time.

As for improvising unknown melodies on whistle, there's just no way to "play quietly"--if I've only got my whistles, I don't play if I don't know the tune, or I just play a low drone on the root note of the current chord.

Just another $0.02, fwiw.

V