When was it--the day before yesterday?--when Mogwai was the hottest new thing? They were young Scots with slow-slow-LOUD panache, forging a new instrumental-rock gateway to the 21st century. So maybe we're a bit complacent after the inevitable midcareer slump ('03's Happy Songs for Happy People). But slumps are relative, and every band has a "hits" collection sooner or later, like this evenly distributed compilation of BBC radio sessions. Most of the material highlights the spellbinding, hypnotic side of Mogwai, from the early ballad of bitter regret "R U Still in 2 It" to "Cody," featuring Stuart Braithwaite's serene, revelatory and rare vocal turn. The first quarter of 18-minute "Like Herod" is Valium-esque as well, but when the Glaswegians finally crank up the squealing, volcanic inferno, it's best to duck for cover and not ask questions. For they shall all be answered by "New Paths to Helicon I," a gorgeous cosmic symphony spotlighting the healing power of the guitar pedal that should go in a time capsule to represent this messed-up time on planet Earth.