As our search for the Holiday Spirit grows increasingly anxious, its lowercase liquid surrogate too often makes do, while Rosemary Clooney assembles in TV pixels to croak Noels, a kid on the radio vocalizes slyly about his mom kissing Santa and a flood of seasonal Muzak saturates the atmosphere. What we perceive, through a glass darkly, is the paradox of offensive good cheer.

The antitoxin to these miseries took about two hours, consisting of 25 brief pieces chosen with great care by J. Reilly Lewis and sung under his direction by the Washington Bach Consort on Saturday night at St. Mark's Episcopal Church with a distinctive, ripened beauty. The purity and flexibility of its sound is attributable to a professional choral ensemble broken free of the usual technical concerns--intonation, balance, integration and all the rest--and intensely responsive to the conductor's personal identification with the spirit animating each composer's music.

Threaded through the program--entitled "In Praise of Mary"--were four rarely heard Christmas pieces Bach omitted from his "Magnificat." Organist Keith Reas warmly introduced them with works from Bach's "Orgelbuchlein," and the duet of soprano Susan Vaules Lin and bass Trevor Ashbarry in the fourth piece was replete with heart-wobbling, joyous conviction. Snapshots taken here and there inevitably distort the concert's subtle symmetries, but Melissa Coombs's limpid, affecting soprano illuminated Jehan Alain's "Ave Maria"; the dark mysticism of Rachmaninoff's "Bogoroditse Devo" ("Rejoice, O Virgin") emerged powerfully; Pierre Villette's "Hymn to the Virgin" twirled with color; and three American carols by Gwyneth Walker, Joel Martinson and John Biggs were vibrantly communicative.