Though it consists entirely of students--undergraduates and graduates at New Jersey's Rider University--the Westminster Choir has been one of America's top choruses for close to six decades. The choir is in residence every summer at the Spoleto Festival in South Carolina, and its 40 members also form the core of the 175-voice Westminster Symphonic Choir, which regularly performs with the New York Philharmonic, the Philadelphia Orchestra, and other major east-coast ensembles. The Westminster Choir's roster changes constantly--every year a significant portion of its singers graduate and leave to start their careers--but under the hand of Joseph Flummerfelt, artistic director and conductor since the early 70s, the group has maintained an enviable aesthetic consistency. Flummerfelt was a protege of the late Robert Shaw, a pioneer in the American choral movement, and learned from him how to integrate singers and instrumentalists (both men have conducted orchestras as well as choruses). When he took over the Westminster, it had passed out of a golden age in the 50s and early 60s, during which it recorded with the likes of Bernstein and Erich Leinsdorf; he quickly restored much of the choir's former glory, developing a well-blended sound, accurate, eloquent phrasing, unimpeachable diction, and a diverse repertoire of 19th- and 20th-century works. (The choir's recent CDs, such as the all-Brahms Singing for Pleasure and Barber's Anthony and Cleopatra, live up to these standards as well.) It's hardly cheap for 40 people to travel, so the Westminster rarely makes it this far west; the occasion for this tour is the group's 75th anniversary. The program includes American hymns and folk songs, as well as classical pieces both well-known (Verdi's Ave Maria, a madrigal from Menotti, three Brahms quartets) and relatively obscure (selections from Poulenc's Quatre motets pour un temps de penitence). I'm looking forward especially to the Westminster's renditions of three of Ives's clever songs; in my opinion, their wordplay and metrical idiosyncrasies can be properly handled only by an American choir of this caliber. Friday, March 22, 8 PM, Fourth Presbyterian Church, 126 E. Chestnut; 312-787-2729, ext. 231.