 As of the 1950s, Cohen was serving as the concertmaster of the orchestras at the Casals festivals in France and Puerto Rico, in addition to several ensembles in New York City including the Colombia symphony orchestra.He was frequently concertmaster for Leonard Bernstein's televised "young people's concerts".His performance As concertmaster under Stravinsky's baton of "The rite of spring" is one of those preserved on the gold album carried by the voyager spacecraft.