Hillyer was born on April 10, 1914, in Ithaca, N.Y.; his mother, Sonia Paeff Silverman, was a pianist and his father, Louis Lazare Silverman, was an amateur violist. He was originally named Raphael Silverman but changed his name in the 1930s to Hillyer, an Anglicized version of a family name. He began studying violin at age 7 and decided to pursue music as a career when he was 10, after, on a visit to Leningrad, taking music courses with Sergei Korgueff and an 18-year-old Dmitri Shostakovich. Hillyer studied at the Curtis Institute of Music and received his undergraduate degree from Dartmouth, where his father was then teaching mathematics. While in graduate school at Harvard, he became friends with Leonard Bernstein, who wrote a violin concerto for him in 1939. 

Hillyer was the last person to join the original J.S.Q., which made its debut at a private concert at Juilliard in October 1946. He had hesitated initially because he already had a full-time job with the Boston Symphony Orchestra under Serge Koussevitzky; earlier he had played with the NBC Symphony under Arturo Toscanini. Then-president of Juilliard William Schuman, who founded the quartet both to be a resident ensemble and to champion contemporary music, asked Hillyer to join. The other members were violinists Robert Mann (Diploma ’39, violin) and Robert Koff (’42, violin), and cellist Arthur Winograd. (Mann is still a Juilliard faculty member.) The group quickly achieved renown, particularly after being the first ensemble to present all six of Bartok’s string quartets as a cycle, in 1949; the quartet also recorded the cycle, in 1950. (The Juilliard String Quartet is scheduled to receive a lifetime achievement award at the Grammy Awards, on February 13.)

Hillyer taught chamber music throughout his Juilliard teaching career, which ended with his retirement from the quartet in 1969; he taught viola here from 1955 to 1967. He also taught at American University, Yale, Curtis, and Harvard. In 1981, he became a viola and chamber music professor at Boston University’s School of Music in, giving his last lecture three weeks before he died. While Hillyer’s last formal performance was last year—for his 95th birthday—he continued to perform privately for friends after that. 

He is survived by his wife Yuko; four children from previous marriages: Nitra Hillyer, of Canandaigua, N.Y.; Linda Hillyer, of Boston; Jonathan Hillyer of Atlanta, and Reiko Hillyer, of Portland, Ore.; and a sister, Freddie Bluhm, of Sydney, Australia.