Herb Pomeroy Big Band--guess what they play? A free Summerthing presentation, Saturday on Boston Common at 8. And, as an extra bonus, a dance demonstration by the Arthur Murray Studios. This could be the sleeper of the weekend. Or just the sleeper.

Geoff Bartley--folk/jazz stuff, at the Back Room at The Idler, 123 Mt. Auburn St., Friday night.

Paul Rishell--country blues, Back Room at The Idler.

Peter Kairo and George Gritzbach--ragtime guitar/blues, at Passim's, 47 Palmer St., Friday and Saturday night.

Con Brio--jazz combo (doesn't mean "with cheese") at the 1369 Jazz Club, Inman Square.