O'Connor composes, arranges, and records American music across genres including folk, classical and jazz. His works include concertos, and compositions for string orchestra, string quartets, string trios, choral music, solo unaccompanied pieces and a new symphony (see Compositions). His "Fiddle Concerto (1992)", a violin concerto in American fiddle style commission by the Santa Fe Symphony Orchestra and Chorus, has been performed over 200 times, making it one of the most performed concertos written in the last 40 years.[8]
In 1997, O'Connor and others composed and performed music based on folk melodies as arrangements in an original score by American modern classical composer Richard Einhorn for the American Revolutionary War-era Public Broadcasting Service documentary miniseries, Liberty! The American Revolution (the companion album is Liberty!). The theme music for the miniseries is O'Connor's "Song of the Liberty Bell.