Playing an electric guitar within the cathedral-like confines of Georgetown University's Gaston Hall borders on blasphemy. So it was only fitting that Dave Mason showed up there last night with nothing more menacing than a 12-string acoustic.

Mason should play this way more often. He and his lone accompanist, guitarist Jim Kreeger, proved at the outset that they weren't going to need an electric booth with their sharply percussive version of "Feelin' All Right." There were times -- owing to Mason's reliance on 12-string guitars and the similar chord patterns that make up his songs -- when the music became tired and listless. But more often, Mason kept things interesting by sprinkling the evening with surprises.

Apart from performing his impressive list of hits including Kreeger's "We Just Disagree," he saluted, with both affection and authority, such diverse musicians as Elmore James, Sam Cooke, Elvis Presley and John Lennon. Bob Dylan's "All Along the Watchtower" displayed not only the compatibility that exists between Mason and Kreeger but also showcased one of their most challenging arrangements.

Chris Smither opened with a set of finger-picking blues, full of gentle slides, sustained notes, sweet, waivering exclamations, humor and emotion.