Let me try this again; I think I started this all wrong.
My friend wants to do a OMB type of product, but he doesn't have any instrumental ability. He's a great singer and does a fine job of conversing with the crowds. He wants to focus on a Polish-American style, but needs backing music. He can easily do a capella, but I feel some sort of MIDI, mp3 setup would be better. Looking for music source suggestions...
cass ... reading your second post made his goal a lot clearer to me ...
I would agree with some of the other comments such as singing at 'open mic' nights, karaoke clubs, etc. so he gets a feel for performing in front of a crowd ...
As far as music accompaniment, in today's environment a lap-top or iPad would certainly suffice, and backing track sites can be found all over the i'net ...
Basically, to me, it sounds like he wants to become a 'karaoke' act ...
Good luck to him ...