I would take the opposite view from GUEST JM and say "go for it".

I had extensive experience of the US immigration system during my years there, and believe me, they ain't that smart.

The chances of being "caught" (by whom ?) and deported are so remote as to be non-existent. To be "caught" somebody would have to actually report you to the immigration service, and that's not going to happen.

This is from one who worked cash in hand for years in the US before becoming legit (and some of it from paid gigs as well).

My advice would be to set up a few house concerts , enter the US on a tourist visa waiver, tell the immigration boys that you are attending a few festivals, just for fun and to jam along, (should they ask about the instruments) and you will be right as rain.