He is credited with bucking the modernist trend in composition, which favored esoteric compositional systems over emotion. According to the Inquirer, it was the death of his son in 1964 that led him away from the music he was beginning to find abstruse.

In a 2001 interview, he said, "[In the 1960s] I ran into New York as often as I could to hear concerts, and it all sounded gray and dull, by people with vast reputations based on what, I'll never know."

His split with modernism brought him notoriety. "I was accused of betraying, in the following order, the church and the state," he said. "I was a traitor, a renegade. I never once responded. If you're going to be a composer, you have to have an iron stomach, fire in the belly, and fire in the brain."

Nevertheless, he became one of the most successful composers of the 1970s and 1980s. Isaac Stern performed his Violin Concerto 47 times between 1975 and 1977, and his string quartets are now standard in American chamber-music repertoire.

Rochberg taught at the Curtis Institute of Music and the University of Pennsylvania, where he was chair of the music department until 1968, and continued to compose well into the 1990s.