Dessoff Choirs at Church of St. Paul the Apostle Willie Davis for The New York Times Dessoff Choirs Christopher Shepard conducting during "Stile Antico" at the Church of St. Paul the Apostle on Friday evening. At intermission Christopher Shepard, the choirs" music director, told the audience that he had been prepared to apologize for "the elephant in the room," a large scaffold that crossed part of the nave. What he had not been prepared for, he added, was the continuing onslaught of amplified sound from the church's basement, where a party had been booked. As for the program, neither the series title, Refracted Bach, nor the concert title, "Stile Antico," entirely covered the ground. The only representations of antiquated style were a Palestrina Mass for six voices, from 1590, and a brief motet, "Sub Tuum Praesidium" by Grzegorz Gorczycki, a Polish contemporary of Bach. That Palestrina work was chosen because Bach made an arrangement of it, doubling voices with cornettos and trombones and adding keyboard. It would have been fascinating to hear Bach-refracted Palestrina, but with few instrumentalists at hand the music was left unadorned. The rest of the program - works by Mendelssohn, Schumann, Sven-David Sandstrom, Knut Nystedt, William Hawley and Ingram Marshall - represented Bach refracted, though in some cases only to the extent that almost everything composed after Bach carries at least some glint of his influence. Choral concert or no, the Marshall pieces for solo instruments, with their sounds manipulated electronically, provided the center of gravity. Libby Van Cleve played that great Bachian instrument, the oboe d'amore, in Mr. Marshall's "Holy Ghosts," with her sound manically echoed. The violinist Todd Reynolds offered "September Canons," a piece written, Mr. Marshall says in a program note, as "a memory piece for the events of Sept. Without overt references, the music gathers a tension finally released in a sort of deconstructive explosion of Bach's Chaconne from the D minor Partita. Still, the ostensible focus was on the choirs, in a series pointing to their performance of Bach's B minor Mass on March 3. To ears recently attuned to New York's finest professional choirs, the sound of this amateur group was not terribly impressive, especially in the Chamber Choir's performance of Schumann's "Talismane," where individual voices were mercilessly exposed. But at least the B minor Mass performance will take place in the Church of St. Mary the Virgin near Times Square, which offers excellent acoustics and, presumably, enough respect for the event that it will not counterprogram, say, Armageddon downstairs. "Refracted Bach" continues on Saturday afternoon with a sing-in of Bach cantata movements at Immanuel Lutheran Church, 122 East 88th Street, Manhattan; (212) 831-8224, dessoff.org.