Amon Tobin made his name with the most distinctive sampladelic electronica in the business, and kept at it for longer than most, but eventually began trading in samples of jazz vinyl for field recordings and bands he's captained. ISAM is his second straight invisible soundtrack, after 2007's Foley Room, and as before, it shows Tobin fascinated with the science of sound. Short on beats but long on atmosphere, ISAM plays out like the soundtrack to some bizarre nature documentary: it continually pauses, goes off in another direction, halts again, then sits unmoving for a time, as though Tobin had been musically ghosting the movements of a tiny insect traveling along a leaf. That's not to say the production is naturalistic; in keeping with his usual style, the beats are massive and speaker-shuddering, but they rarely coalesce into a specific pattern. It shouldn't come as a surprise that Tobin succeeds despite this challenging rubric; ever since he began dabbling in video-game soundtracks, he's showed an intriguing resilience at making excellent music no matter what challenges he places in his way.