Siegfried earned his bachelor's degree at Antioch College. He then attended the University of Iowa, where he received a master's degree in theory and composition; among his professors was Donald Martin Jenni. He completed a doctorate in composition at the New England Conservatory of Music, where his instructors included Lee Hyla, Michael Gandolfi, and Daniel Pinkham. He also studied in France and in India, where he received a Stanley Fellowship to study South Indian classical music with Sriram Parasuram. He has received grants and awards from ASCAP, the National Endowment for the Arts, and the New Hampshire State Council on the Arts, among other organizations. He currently lives in Andover, Massachusetts. At the Boston Conservatory at Berklee, he is a Professor of Theater, and Coordinator of Theory and New Works. In 2017, he was the winner of Berklee's Distinguished Faculty Award.
Siegfried is especially noted for his work with the music of the Shakers, which he first encountered in 1995 during a visit to the Shaker village at Pleasant Hill, Kentucky. He has since produced many choral arrangements of Shaker songs, and has composed a cantata, Angel of Light, for which they served as a basis. He has been associated for some time with Canterbury Shaker Village in New Hampshire, and Sabbathday Lake Shaker Village in Maine, as of 2017 the home of the last living Shakers. Siegfried's arrangements of Shaker music have been recorded by the Tudor Choir and the Dale Warland Singers. He has also written works for the Nashua Symphony Orchestra in Nashua, New Hampshire.
Siegfried's music is published by G. Schirmer, E. C. Schirmer, Earthsongs, MorningStar, and Trinitas.