Jim Seals of Seals & Crofts died on Monday at age 80, according to friends and family. The cause of death wasn't immediately released.

Seals was the principal lyricist and singer behind eight Top 40 hits in the '70s. Seals & Crofts rose as high as No. 6 on the singles chart three times, with 1972's "Summer Breeze," 1973's "Diamond Girl" and 1976's "Get Closer." He'd stopped playing music in 2017, after reportedly suffering a stroke.

“My heart just breaks for his wife Ruby and their children,” cousin Brady Seals of the country band Little Texas told Variety. “Please keep them in your prayers. What an incredible legacy he leaves behind.”

Born in 1942 at Sidney, Texas, to oilman Wayland Seals and his wife Cora, James Eugene Seals began his career as a member of the Champs with Glen Campbell, joining after they hit with "Tequila." He toured with Eddie Cochran before initially working with Dash Crofts during a subsequent stint with Campbell. They built their career show by show, while Seals & Crofts' first three albums were largely ignored.

"We were lucky," Seals told Melody Maker in 1975. "We came along at a time when Chicago, Jethro Tull and the Moody Blues and people like that would have us as a support band."

"Summer Breeze" became their breakout hit. Suddenly, Seals & Crofts were huge stars – and the subject of no small amount of derision from some rock critics. (Robert Christgau memorably dubbed them "folk-schlock.") They kept selling records while delving into surprisingly philosophical subject matter, including the often-misunderstood Bahai faith.

Listen to Seals & Crofts' 'Summer Breeze'

Both 1975's "I'll Play for You" and 1978's "You're the Love" went to No. 18, and Seals & Crofts even appeared at the California Jam alongside the likes of Deep Purple and Eagles. By the time they broke up amid the rise of disco, punk and post-punk, Seals & Crofts had notched four gold-selling albums and a pair of multiplatinum LPs, including 1975's Greatest Hits.

“We were still drawing 10,000 to 12,000 people at concerts, but we could see, with this change coming where everybody wanted dance music, that those days were numbered," Seals told the Los Angeles Times in 1991. "We just decided that it was a good time, after a long run at it, to lie back and not totally commit ourselves to that kind of thing.”

Jim and Ruby Seals moved to Costa Rica, where they raised three children while operating a coffee farm. Seals & Crofts finally reunited 11 years later and again in 2004 when they released Traces, their first new album since 1980's The Longest Road.

Seals was the older sibling of the late Dan Seals, who found fame as part of England Dan & John Ford Coley. The brothers later toured together as Seals and Seals.

"It was because of Jimmy opening doors for us that we came to Los Angeles to record and meet the right people," Coley said in an emotional Facebook post. "This is a hard one on so many levels as this is a musical era passing for me. And it will never pass this way again as his song said. He belonged to a group that was one of a kind."

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