“It felt like nobody really trusted me,” he recalled of this time in a 2015 interview. “I would go to the orchestra rehearsal, playing along, and my colleagues were going, ‘Yeah, but you also do that strange contemporary music, you play John Cage.’ And then I would go to a hard-core new music thing, and they’d go, ‘Yeah, you’re really not one of us because you also play in an orchestra.”

But, inspired by his longtime partner, the composer James Sellars, as well as the pianist Yvar Mikhashoff, Mr. Black increasingly dedicated himself to contemporary composition, at a time when few classical virtuosos were committed to new works. An early showcase was Mr. Sellars’s “For Love of the Double Bass,” a piece for bass and piano that combines music and theater, in which Mr. Black seduced his instrument, buying it a dress, dancing with it and ultimately taking it to bed.

As part of the Bang on a Can All-Stars, Mr. Black helped popularize experimental music through international tours and well-regarded albums. He and the guitarist Mark Stewart, the only two original members to remain with the sextet, performed together for more than three decades.

“He was deeply kind, often playful, gently yet fiercely devoted to the composer and his colleagues onstage,” Mr. Stewart wrote in an email. “His humility was real because his wisdom came from listening.”

Mr. Black also pursued a solo career, building a sizable new repertoire for his instrument and recording the complete bass music of Giacinto Scelsi and Christian Wolff. A dedicated pedagogue, he taught at the Hartt School for 29 years. In 2017, he formed the Robert Black Foundation to support contemporary music. He frequently commissioned work from young and emerging composers, whose music he performed as part of a monthly Friday series during the pandemic, live-streamed from his home.