He studied music composition and theory at the State University of New York at Buffalo with Lejaren Hiller, Lukas Foss, and István Anhalt, receiving his BA in Music (1969) and MA in Music Composition and Theory (1971). From 1972–2003 Horwood was a professor of music and humanities at Humber College of Applied Arts and Technology in Toronto. During the latter half of the 1970’s, Horwood formed Convergence, an improvisation ensemble in which he played piano and percussion. In 2003 he retired from teaching and with his wife moved to Cowley, Alberta.