Joel Krosnick, the longtime cellist of the Juilliard String Quartet, who helped shape its championing of new American music as much as its commitment to the classics, died on April 15 at his home in Hastings-on-Hudson, NY. He was 84.

Mr. Krosnick joined the Juilliard in 1974 and remained until his retirement in 2016. With his longtime musical partner, the pianist Gilbert Kalish, Mr. Krosnick also had an active solo career, giving recitals in the United States and Europe.