It was possible to escape from the stresses of the 21st century Thursday evening by ducking into St. Mark's Episcopal Church, where a sextet of musicians performed 18th-century concertos on period instruments for the Capitol Hill Chamber Music Festival's concluding concert.

Flutist and festival artistic director Jeffrey Cohan selected two unpublished baroque concertos from the Library of Congress to complement the Bach family compositions on the program. Johann Tromlitz's Concerto III in C featured Cohan, whose woody, recorder-like tone was so soft one had to lean forward to hear its elusive melodies. His sound was buoyed by violinists Risa Browder and Leslie Nero, violist Steven Creswell, cellist John Moran and harpsichordist Dongsok Shin -- a last-minute replacement for J. Reilly Lewis, who was sporting a thumb splint.

C.P.E. Bach's heavily accented Concerto in A Minor engaged the instruments in a dramatic dialogue. But in Johann Joachim Quantz's Concerto in E Minor, it was the rubbery harmonies of pizzicato strings with flute that beckoned.

For much of the evening, the harpsichord maintained a basso continuo gait beneath the group. However, in J.S. Bach's "Brandenburg" Concerto No. 5, Shin finally gained the lead. He sustained the midsection passages with shimmering energy as air suspends a glider, swooping with the modulations into a flashy cadenza. After a reflective second movement with Shin and violinist Browder, Cohan led the way, nearly dancing, in the celebratory finale. Fortified by such a pleasant performance, listeners slipped back into the present, humming melodies three centuries old.

-- Grace Jean