Back in the late 1980s, Bobby McFerrin unveiled his sensational a cappella vocal group Voicestra, but the peripatetic singer/composer (and now conductor) waited nearly a decade before putting anything out in that concept, and on a classical label yet! Taking the lead, the rubber-voiced McFerrin sets up revolving wordless vocal patterns, and he and the group improvise what amount to eight individual mantras.

The songs have no titles -- only "Circlesong One," "Circlesong Two," et al -- yet they use all kinds of African, Middle Eastern, and other vocal or vocal percussive techniques, as well as studio production embellishments, to shape them after the fact.

The 12 singers in this Voicestra are a freely eclectic mixture of R&B, gospel, pop, and jazz vocalists (including the Manhattan Transfer's Janis Siegel), performance artists, opera and classical singers, yet they blend together in an astonishingly homogenous manner when used in this fashion.

The first "Circlesong" is the most immediately fetching, built around a single riff as McFerrin hollers and moans over the shifting voices, but all of them contain some amazing ideas, and at a mere 42 minutes, the album does not wear out its welcome as it might have, had McFerrin stretched the music out to the usual CD length.

It's hard to figure out what category to put this disc in -- maybe next to Ladysmith Black Mambazo on the world music shelf -- but labels don't matter in a soundworld with this much imagination and heart.