Depends on the clientele. If the bands are playing head-banger music, then the fans expect to hear the same stuff in between sets; so Dolly Parton would not be the right fit!

After you've got the right genre/style of music set, then I'd recommend putting on songs with upbeat lyrics versus anything that makes you want to jump off a building. Of course you've not identified what you are trying to sell - drinks, tickets to other concerts, or conecerts in outside venues.

Certainly the music choice can help you "push" bar drinks if everyone feeling good, but so can announced half an hour discounts. And if it's other stuff you want to sell - like t-shirts ( or tickets as I said before) then you'd need to break up the music with some hard calls to action, like "Buy a t-shirt in the next half an hour and get a buck ( or two) off your next drink."

Best of luck!