As a duo, superpickers Darol Anger and Mike Marshall have sometimes lacked a strong rhythmic bottom, but that has been solved. They've expanded to a quartet that includes Barbara Higbie, a very percussive pianist, and McLean's Michael Manring, a very melodic bassist.

Dubbed the Montreux Band, after the Swiss jazz fest where they first appeared, this quartet made its area debut at the sold-out Wolf Trap Barns Friday night and immediately established itself as one of the top bands in the new acoustic music field. The inventive excursions of Anger's fiddle and Marshall's mandolin were continually pulled back into the main theme by the gravity of Higbie's grand piano and Manring's fretless electric bass.

All four members are impressive composers, and this background made them more attuned to the overall shape of each piece instead of individual solos and fills.

Marshall's "Tidepools" had a restrained, reflective feel sustained by Anger's extended fiddle lines. Higbie proved not only a smart, solid jazz pianist, but she also delivered a smoky jazz reading of her own lyrics to Django Reinhardt's ballad "Anouman." Manring's Virginia collaborator, Bobby Reed, added his supple soprano sax to the band for four songs. Mark O'Connor, a former colleague of Anger and Marshall and the David Grisman Quintet, played a rather dry, unaccompanied opening set. He then joined the band for two exhilarating encores: a four-fiddle jam, and a six-piece romp through chunky rhythms and playful tangents.