Born in San Juan, Puerto Rico, violist Janz Castelo is the son of Cuban parents. He received his bachelor of music in viola performance from the Peabody Conservatory of Music as a student of Victoria Chiang and Roberto Diaz. Upon completing his degree, Janz continued his studies with Boston Symphony violist Edward Gazouleas. Janz joined the viola section of the Buffalo Philharmonic Orchestra in the fall of 2001 and the faculty of the University at Buffalo in 2005. In the fall of 2007, he formed the Buffalo Chamber Players, a mixed chamber ensemble residing in the Elmwood Village.
In Boston, Janz held teaching positions at The Cambridge School of Weston and The Dana Hall School of Music and was Assistant Principal Violist of the Portland Symphony Orchestra in Portland, Maine. He has appeared in music festivals in the United States and abroad, including the National Orchestral Institute in Maryland, the Yellow Barn Chamber Music Festival in Vermont, the New Hampshire Music Festival, and the Kuhmo Chamber Music Festival in Kuhmo, Finland.