The word "upbeat" has always been hard to avoid when describing the sound of Belle & Sebastian [ tickets ]--not to mention "lush," "poppy," and even "fey"--but on their sixth album the Glasgow, Scotland-based septet pushes all of these adjectives to another level.

What has made this band unique from its start--a blend of influences ranging from Paul Simon to Morrissey, with elements of '60s acoustic folk, '70s-disco strings and '80s horns--is still here, but richer and more fully conceived. The album rollicks from the beginning with "Step Into My Office, Baby," full of a "Good Vibrations"-like bass-line and groove, proceeding with the usual pub-fare ballads--like "Lord Anthony"--but now with a chamber-orchestra sound. Others, like "Wrapped Up in Books" and "Piazza, New York Catcher," echo the best of the band’s earliest albums, while "Roy Walker," with its spoken vocals over snapping fingers, could easily have been ripped from a Broadway musical.

For a group that often melds sad, wistful lyrics with lighter melodies, Belle & Sebastian, with their effervescent leader Stuart Murdoch, seems especially happy here. Luckily, the band layers the songs on "Waitress" with enough depth and storytelling that there is much beyond its "upbeat" veneer.