Pentangle, on its first American tour in 14 years, proved Thursday night at the Birchmere that the lapse of time has only deepened the qualities that made this British quintet one of the most influential ensembles in Anglo-American folk music. The vastly underrated Bert Jansch, a powerful guitarist and singer, was more than ever the leader of the group. He played a dazzling guitar piece, "Angie," and lent his haunting, droning baritone voice to his gorgeous new song "The Open Sea."

But Pentangle was anything but a one-man show. Jacqui McShee's bell-tone soprano brought out the refined melodies of the traditional Irish and Scottish ballads, and her melancholy tone brought out the lyrics' sense of yearning and loss. Drummer Terry Cox, often switching from sticks to mallets in the same song, imposed a crisp jazz swing on the Brazilian instrumental "Kingfisher." Mike Piggott proved a satisfying replacement for John Renbourn as Jansch's instrumental foil; Piggott's electric guitar fills on "Bruton Town" and his bold sweeping fiddle lines on "Dragonfly" pushed Jansch to his limits. Newcomer Nigel Smith replaced Danny Thompson's acoustic jazz bass with his own fretless electric jazz bass, which lent bluesy slides and dark colors to the impressively cohesive ensemble effort.