With their full-dose mix of guitar spaghetti, electronic beats, and ambient flotation devices, the Biscos have clandestinely become the most thrilling live act in jam-band-land. While 2001’s ”They Missed the Perfume” pushed their techno-Phish fusion into sprawling, uncharted territory, Boombox focuses on ”songs,” never the band’s strong suit. The result is odd-metered, art-rocked, and often wanky. But when all jam-jets are firing (see ”Floes”), you’ll forgive them everything. Almost.