Carla Bley, the influential pianist, composer and bandleader who was an important figure in the avant-garde jazz movement of the 1960s, has died. She was 87.

Bley’s partner, the bassist Steve Swallow, confirmed to The New York Times that she died Tuesday in Willow, a hamlet in upstate New York. He said the cause was complications from brain cancer.

Among Bley’s best-known works was her 1971 jazz opera Escalator over the Hill, performed by the Jazz Composer’s Orchestra, which she founded with trumpeter Michael Mantler. Bley’s compositions have been performed by many other artists, including Gary Burton, Art Farmer, John Scofield, Jimmy Giuffre, George Russell, and her former husband Paul Bley.

Bley also stood out as one of the few women of her era to become known as an instrumentalist, composer and bandleader, rather than a vocalist. Not only that, she emerged as a leader among her peers when she and Mantler created the Jazz Composers’ Guild, pioneering the development of independent, artist-owned recorded labels and helping to broaden the distribution of recordings of what they called “creative improvised music.”

Born Lovella May Borg on May 11, 1936, in Oakland, Calif., Bley was encouraged by her father Emil Borg, a piano teacher and church choirmaster, to sing and play the piano. When she was 17, she moved to New York and became a cigarette girl at Birdland, where she met jazz pianist Paul Bley. She toured with him under the name Karen Borg, before she changed her name to Carla Borg in 1957. She married Paul Bley the same year, then adopting the name Carla Bley. The couple divorced in 1967, but she kept his surname professionally.

Throughout her career, Bley considered herself a composer, first and foremost. Early on, several musicians began to record Bley’s compositions. George Russell recorded “Bent Eagle” for his 1960 album Stratusphunk; Jimmy Giuffre recorded “Ictus” for his 1961 album Thesis; and Paul Bley used six of her compositions for his 1965 album Barrage.

In 1964, Carla Bley and Michael Mantler founded the Jazz Composers Guild, bringing together many of New York’s boundary-pushing musicians. Their relationship continued both professionally and personally; they had a daughter, Karen Mantler, who became a musician herself. They were married from 1965 until 1991. Together, they led the Jazz Composers’ Orchestra for many years. They also founded the record label JCOA, which released a number of historic recordings by Clifford Thornton, Don Cherry and Roswell Rudd, as well as Bley’s Escalator Over the Hill and Mantler’s The Jazz Composer’s Orchestra series of albums.

Over the course of a more than 60-year career, Bley recorded nearly 30 albums as a leader, six with the Jazz Composer’s Orchestra, and more than a dozen as a co-leader with Michael Mantler, Charlie Haden and the Liberation Music Orchestra, Gary Burton, Nick Mason, and Steve Swallow. Her compositions were recorded by other artists more than 80 times.

Bley was awarded a Guggenheim Fellowship in 1972. She was named an NEA Jazz Master in 2015.