Doc Watson, the great blind banjo and guitar picker, is appearing at the Performance Center I this week with Geoff Muldaur. Watson played in Cambridge this spring and was a resounding success; country music seems to be getting popular in Cambridge at last. Geoff Muldaur is Maria's husband (or maybe ex-) and a holdover from the early-sixties folk scene; according to popular legend, when he was a teenager he hitchhiked from Boston to East Texas with a broom to sweep off the grave of an obscure early bluesman. In any event, he used to perform in a duo with Maria but since her recent success she seems to have left him to fend for himself. Watson is certainly worth going to see on his own, and Muldaur could be a pleasant surprise. July 2, 3 and 4 at 8 and 10:30.

Charles Lloyd will be at the Performance Center II playing free-form sax and flute, probably in a quartet including piano, bass and drums. Lloyd started out in the fifties and hit it big on a European tour in the mid-sixties, when he had Keith Jarrett and Jack DeJohnette in his band and first branched out into improvisational stuff. Lloyd's salad days are apparently over now and his music can get pretty atonal at times, but he'll at least put on an unusual show.

Jerry Butler, the Iceman, is appearing over in Boston at Paul's Mall. Butler has produced some nice, smooth R&B singles, notably "Only the Strong Survive," but lately he has been veering dangerously in the direction of middleaged pop music as well. He'll probably stick with slick soul material at Paul's Mall, though. July 2 through 7.

Jimmy Smith is making a week-long stand next door at the Jazz Workshop, the best jazz place in town. Smith goes way back--he got his start playing organ in the bop era, and is now arguably the best jazz organist around and certainly one of the most durable. His "Hootchie-Cootchie Man" and "Got My Mojo Working" are classics. Smith usually plays in an organ-guitar-drums trio, but the personnel varies. Along with Watson, this sounds like the week's best music bet. July 1 through 7, call 267-1300 for times here and at Paul's Mall.

David O'Docherty, an obscure pipes-and-flute man, will sing traditional Irish and English songs and ballads at Passim's, the last surviving folk coffee house in the Square. It sounds offbeat; Passim's usually has more conventional guitarfolk music. July 2, 8:30.