Richard Wright, who died yesterday at 65, was a co-founder of Pink Floyd. His brooding yet sometimes jazzy organ licks were an integral part of the band’s trademark melancholy sound.

His death from cancer, coming two years after former lead singer Syd Barrett’s, leaves just two original members of Pink Floyd: guitarist Roger Waters and drummer Nick Mason.

Wright is heard all over Pink Floyd’s “Dark Side of the Moon,” the 1973 album that has sold more than 40 million copies. He later helped create the group’s epic compositions such as “Echoes” and “Shine On You Crazy Diamond.”

Conflicts with Mr. Waters led to Wright’s departure from Pink Floyd during recording sessions for “The Wall,” the band’s portentous 1979 rock opera.

“Roger’s ego was getting bigger and bigger,” he told the Boston Globe in 1997. “He said he wanted me out because I hadn’t produced any material: ‘If he doesn’t leave, I’m going to withdraw “The Wall” and make it a solo project.’ Dave [Gilmour] and Nick Mason, the drummer, were very scared, too. It was a nightmare for all us.”

He was brought back as a contract musician for the subsequent tour and formally rejoined Pink Floyd only after Mr. Waters left in 1985.

He appeared on the band’s later releases: “A Momentary Lapse of Reason” (1987) and “The Division Bell” (1994).

Richard George Wright was born July 28, 1943, in London. His father was a biochemist.

Self-taught as a musician, he studied architecture at Regent Street Polytechnic while playing in the early 1960s folk and blues scene in bands with fellow students Mr. Mason and Mr. Waters. Pink Floyd arose out of several earlier bands with names including the Tea Set and the Screaming Abdabs, many of them featuring guitarist and vocalist Barrett. The band was originally dubbed The Pink Floyd Sound, combining the names of two of Barrett’s musical heroes.

“When we were with Syd, our ambition was probably to get a number one hit, to get on Top of the Pops,” he told Britain’s Independent in 2006. “My only ambition was: This is fun, I hope we can make a living out of this. And of course, I hope we’re gonna be a huge success and sell more records than Elvis Presley and the Beatles!”

Though the band’s influential first record “The Piper at the Gates of Dawn” was recorded at Abbey Road studios at the same time “Sgt. Pepper’s Lonely Hearts Club Band” was being recorded, Pink Floyd was no sales threat in the early days to the Beatles. But “Piper” did establish Pink Floyd as a leading psychedelic band and set the stage for later releases, including “A Saucerful of Secrets” (1968) and the jam-packed “Ummagumma” (1969).

Wright released two solo albums, including “Broken China” (1996), inspired by his wife’s successful battle with depression. The singer Sinead O’Connor appeared on two tracks, “Reaching for the Rail” and “Breakthrough.” Wright insisted that the album differed from typical Pink Floyd in that it had a happy ending.

“Roger Waters was certainly preoccupied with the dark side of life,” Wright told the Chicago Tribune in 1997.

Pink Floyd reunited in July 2005 to perform at the Live 8 benefit concert at London’s Hyde Park.

Wright complained in an interview with the Independent about how appearances at Live 8 by Victoria and David Beckham seemed to detract from the music.

“But apparently when Pink Floyd went on, the whole backstage area was empty! Which says something,” Wright said. “And it was really nice that we did get onstage again with Roger, because it was a good cause — the cause was more important than our arguments with each other. But I doubt very much whether we’d all four of us get on the road again and do a huge tour.”

Cataract surgery prevented Wright from attending the band’s induction in the UK Music Hall of Fame, later in 2005.