Keith, not sure I take your meaning correctly. Sounds like you don't
like harmonicas (I wonder why you're on this list if that's the
case?). ;-)
Playing a number of the same instrument in unison can be exceedingly
tedious, to be sure.
The goal is to use different TYPES of harmonicas, and to play
different PARTS (just as you would in a more conventional band), i.e.,
rhythm, bass, accompaniment, melody, harmony, etc.
Even then, it could still get tedious, if players don't have the most
crucial attribute: big ears. Imagine playing a 6-string, 12-string,
dobro & bariutone guitar all in the same band. It CAN be done, but
only carefully.
I play in a few performance situations. I've found if players aren't
listening to one another, it's a train-wreck. High-volume & running-
off-at-the- er, instruement are the biggest challenges I face all the
time.
"When in doubt - lay out."
C