Richard Tandy, the keyboardist for the British rock band Electric Light Orchestra, who helped shape the futuristic blend of Beatles-esque pop and orchestral arrangements that catapulted the group to global fame in the 1970s, has died. He was 76.

His death was announced by Jeff Lynne, the band’s frontman and leader, in a social media post. Mr. Lynne, who called Mr. Tandy his “longtime collaborator,” did not specify when Mr. Tandy had died or the cause of death.

Born on March 26, 1948, in Birmingham, England, Mr. Tandy joined E.L.O. after the release of its first album in 1972. He initially played bass guitar but became the group’s keyboardist after another member left.

Mr. Tandy remained a core member of the band through ever-changing lineups, alongside Mr. Lynne and the drummer Bev Bevan, until it disbanded in 1986. He was Mr. Lynne’s “multi-instrumentalist, co-orchestrator and valued musical partner,” the Rock & Roll Hall of Fame said when it inducted E.L.O. in 2017. When Mr. Lynne revived the band in the 2000s, Mr. Tandy was the only other longtime member to participate.