<<how best to capture acoustic style diatonic playing WITHOUT cupping the
microphone both live and in the studio.>>
Just a shade off topic, and perhaps not:
I'm mainly an acoustic player. I do alot of different kinds of hand
flutters for different kinds of vibratos when I'm playing live.
Almost none of them work the same way in front of a studio mic. Where I
cup my harp hand and cover it and uncover it completely with the other when
playing live, I find I get the same effect in the studio by never covering
the cupped hand much at all, and just moving my free hand back and forth
about an inch.
I don't know if this has been anyone else's experience, but a full on
cupped vibrato sounds totally wrong to me when recorded.