Seymour Barab, a composer known for his whimsical chamber operas on such stirring subjects as passion, poison and pizza, died on June 28 in Manhattan. He was 93.

His wife, Margie King Barab, confirmed his death.

Originally renowned as a cellist, Mr. Barab was a lifelong champion of contemporary music. He was a founding member of the Composers String Quartet, established in the mid-1960s with the violinists Matthew Raimondi and Anahid Ajemian and the violist Bernard Zaslav.

The quartet, based for many years at Columbia University, was renowned for performing the work of 20th-century American composers like Elliott Carter, Milton Babbitt and Ruth Crawford Seeger.

As a composer, Mr. Barab was most famous for vocal works, including settings of texts by writers as diverse as Dryden, Yeats and Kurt Vonnegut. Recordings of his vocal music include the “Cosmos Cantata” for singers and chamber orchestra, with text by Vonnegut.