Early on as a student—first at the New England Conservatory, then at The Juilliard School—Danielpour established his reputation as a pianist (studying under Hollander, Jochum, and Chodus) and composer (under Persichetti and Mennin). His first Piano Concerto, completed in 1981 (but later withdrawn), was commissioned and received its first performances while Danielpour was still a Juilliard student. He initially employed serial methods in his works in the early 1980s, but works from the end of that decade, such as First Light (1988) and The Awakened Heart (1990), adopt a broader and more expressive style. He emerged in the 1990s as one of a handful of composers, alongside Adams, Rouse, Schwantner, Corigliano, and Kernis, who embraced triadic harmony alongside experimental innovations of the previous century — the familiar sound of the traditional orchestra as well as elements of pop, rock, and jazz. 1996's Concerto for Orchestra ("Zoarastrian Riddles"), for example, contains musical allusions to Broadway scores, movies, and television. In the late 1990s, Danielpour became one of only three composers (the others being Stravinsky and Copland) to be signed to an exclusive recording contract with Sony Classical. He has fulfilled commissions for numerous orchestras including the San Francisco Symphony and the New York Philharmonic, received several awards (including MacDowell, Rockefeller, and Guggenheim fellowships), completed numerous residencies, and served on the faculties of the Curtis Institute and the Manhattan School of Music. In 2005 he completed his first opera, Margaret Garner, in collaboration with Toni Morrison.
In common with many other American composers of the post-war generation, Danielpour began his career in a serialist milieu, but rejected it in the late 1980s in favor of a more ecumenical and "accessible" idiom. He cites the Beatles—along with John Adams, Christopher Rouse, and Joseph Schwantner—as influences on his more recent musical style. He also makes frequent references to Hemingway and Whitman, saying the emotion in prose and verse can be translated to music. Danielpour's notable works include First Light (1988) for chamber orchestra, three symphonies (1985, 1986, and 1990), four piano concerti (1981, 1993, 2002 and 2009), the balletAnima mundi (1995), and the opera Margaret Garner (2005).
three arias from Danielpour's 2005 opera Margaret Garner; commissioned by the Wheeling Symphony, who premièred the work with soprano soloist Tracie Luck and André Raphael Smith conducting in Wheeling, WV on 19 May 2006.
Voices of Remembrance (2006), concerto for string quartet & orchestra