At Columbia Union College in Takoma Park, the Friday evening concerts take place in the Sligo Church, which is attached to the campus. They are called "Friday Night Vespers," and they open with a prayer: "Peace be with us; peace be with the musicians as they play." After the first piece, there is another prayer and a collection is taken.

At first, the experience can unsettle musicians who are not ready for it. Last night for a while, it seemed to unsettle cellist Diane Chaplin and pianist Gretchen Saathof. But eventually peace was with them, problems of balance were overcome and they settled in for an evening of enjoyable music-making with a program made up mostly of seldom-heard repertoire.

The Sligo Church concert series is one of the newer examples of a fine old tradition in the Washington area: chamber music in churches. Look around a bit, and you can find it happening in dozens of them--evenings and weekends in residential areas, sometimes during lunch hours on workdays downtown. It is also part of a trend toward professional chamber music in the suburbs. Places like the Sligo Church, the Twinbrook Library in Rockville and the Reston Community Center are slowly opening new outlets and finding new audiences for live chamber music--mostly people who are not habitue's of the Kennedy Center and the Library of Congress. They also give experience (and a bit of money) to young musicians.

Chaplin is young but already well experienced in both chamber and orchestral music. Last night she displayed a rich, mellow tone, a fine sense of cantabile phrasing and a clear affinity for romantic repertoire in three unfamiliar works: the Sonata in D, Op. 31 of Joseph Wo lfl, the Romance and Scherzo, Op. 22 of Arthur Foote and David Popper's Polonaise de Concert, Op. 14. She gave a good account of the virtuoso fireworks of Benjamin Britten's Sonata in C, Op. 65, though virtuosity does not seem to be her chief interest. Tchaikovsky's Variations on a Rococo Theme, played in the Washington area for the second time in less than a week, sounded more interesting last night than it did on Monday evening when Sharon Robinson played it at the Kennedy Center.