When we arrived at the Middle East on Saturday night, Brad Caetano was on stage alone, with borrowed equipment, drumming up a storm over his looped guitar. Throughout AM/PM's opening set, which was later fleshed out with bass and saxophone, Bostonist could hear the usual Downstairs conversations roaring in the back of the room but, up front, the mood was that of a seance, interrupted only by appreciative mid-song applause. We, too, found ourselves......