On Tortoise’s fifth album, It’s All Around You (Thrill Jockey), the group makes its most explicit homage yet to ECM’s solemn, hushed jazz tropes. The Chicago quintet has always revered jazz’s elites and peppered its albums with improvisational flurries that leave its postrock peers in the dust. Eleven years into its career, Tortoise plays with as much telepathy and skill as ever, but its inspiration has waned. The fire in the belly has flickered to an ember. Guitarist Jeff Parker sounds excessively polite on most of the disc, pealing off blase Santana-like spectral arcs and Pat Metheny-esque pointillist notes (only on “Dot/Eyes” and “Five Too Many” does he really sting). On a positive note, John McEntire’s and John Herndon’s drums are remarkably recorded and their rhythms are deft with tricky meters, and Tortoise’s trademark marimbas resonate and undulate with requisite mellifluidity. However, despite the band’s obviously righteous chops, Tortoise is becoming a Muzak version of itself, the mellow jazz docent about whom the rock band Pavement disdainfully sang on Perfect Sound Forever. But, damn, the CD cover’s gorgeous.