He is distinguished professor at the Graduate Center of the City University of New York.
Treitler studied at the University of Chicago, earning a B.A.
He earned his MFA from Princeton University (1960) and a Ph.D. (1967); there he studied under Oliver Strunk, Arthur Mendel, and Roger Sessions.
Treitler's major work is in Medieval and Renaissance music, particularly in Gregorian chant and the earliest polyphony.
He revised Oliver Strunk's Source Readings in Music History in 1998.