 Over the course of years, younger performers who had "learned the ropes" with the Group formed their own ensembles patterned on it; one outstanding example of this is Speculum Musicae, which was formed in 1971.A broad range of composers was represented by the Group over the course of its first 25 years.A brief (but not exhaustive) list includes Edgard Varèse, Elliott Carter, Milton Babbitt, Igor Stravinsky, Béla Bartók, Donald Martino, Peter Westergaard, Benjamin Boretz, Otto Luening, Vladimir Ussachevsky, Mario Davidovsky, Goffredo Petrassi, Stefan Wolpe, Ursula Mamlok, Ralph Shapey, Karlheinz Stockhausen, Pierre Boulez, Luciano Berio, Harley Gaber, Alban Berg, Arnold Schoenberg, Anton Webern, Harrison Birtwistle, Peter Maxwell Davies, Ezra Laderman, Raoul Pleskow, Elaine Barkin, Arthur Berger, Yehudi Wyner, Bülent Arel, Joji Yuasa, Toru Takemitsu, Francisco Kropfl, Jeffrey Kresky, David Olan, Goffredo Petrassi, Aaron Copland, Morton Gould, Frederick Fox, Ross Lee Finney, Roger Reynolds, Robert Stewart, Jacob Druckman, Bernard Rands, Robert Hall Lewis, Claudio Spies, John Harbison, Joan Tower, Chester Biscardi, Carlos Salzedo, Lukas Foss, and Richard Edward Wilson.