On his return from Korea, he continued his post-graduate studies at Harvard University where he received a PhD in composition in 1972 with The Sleepwalker's Ballad, "an accompanied recitative for soprano and chamber ensemble".
March 1990 saw the world premiere at Symphony Hall, Boston of Sur's most famous work, Slavery Documents, an oratorio for 80 voices with a libretto by the composer.
[4] In 2008, John Harbison, who described his friend as having "a unique ear for the incantatory power of percussion instruments",[5] composed Cortège for six percussionists: In memoriam Donald Sur as a tribute to him.
Sur also composed the score for Dai Sil Kim-Gibson's 1999 film Silence Broken, a documentary about the Korean "comfort women" of World War II.
Sur wrote the libretto himself based on a variety of texts and documents relating to slavery, including passages from the Bible, Cotton Mather's The Negro Christianised, the 1831 confessions of Nat Turner, descriptions of slave punishments published by the American abolitionist Theodore Weld in American Slavery As It Is, pre-Civil War advertisements for runaway slaves, Negro spirituals, and Stephen Foster's sentimental ballad "Old Folks at Home".
The Boston Globe critic Richard Dyer noted "some peculiar and unconvincing stresses in the setting of the text, some music that sounds merely bombastic, and some unidiomatic writing for the soloists in difficult registers," but found the piece emotionally powerful and concluded that "the flaws are not important in the context of an overwhelming achievement.
He echoed Dyer's comments about the setting of the music for the soloists but also found that Sur's "attempts to incorporate vernacular idioms and historical styles failed to resonate: they were just stuck onto the score, ornamentally, without development or conviction.
It contains Red Dust; Catena I, II, and III; The Unicorn and the Lady; Berceuse; Satori on Park Avenue; and A Neo-Plastic Epistrophe While Crossing Times Square.