The composer Peter Lieberson died on Saturday, age 64, of cancer, five years after the death of his wife, Lorraine Hunt Lieberson.

His recent “Remembering JFK,” which the NSO gave its world premiere in January, was a functional occasional piece that was far from representing his best work. The Neruda Songs that he wrote for his late wife were, by contrast, a significant and moving achievement, and show how he, and she, should be remembered.