Longtime manager Tony Gottlieb said Seals, diagnosed with lymphoma two years ago, died Wednesday night at his daughter's home in Nashville.
With England Dan and John Ford Coley, Seals had hits including "I'd Really Like to See You Tonight" and "Nights Are Forever," both in 1976. His country hits in the '80s and '90s included "Bop," ''You Still Move Me," ''Love on Arrival," and a duet with Marie Osmond, "Meet Me in Montana."
"I've loved to play and sing from the moment I knew what it was," he told The Associated Press in 1992.
Seals, who is survived by his wife and four children, was in hospice care when he died.
"He was very positive," said Gottlieb, Seals' manager for about 30 years. "He participated in several clinical trials to assist with research on this type of lymphoma."
Gottlieb said a major misconception about Seals is that he was a pop singer who came to country music. In reality, he said, Seals grew up singing country music and crossed into pop.
"He was raised in a very rural part of West Texas. His father was an amateur country singer, and he used to play with his dad. They were Hank Williams, Grand Ole Opry people. He was much more of a country singer than a pop singer."
Seals' older brother, Jimmy, was the Seals in Seals & Crofts, who recorded the hits "Summer Breeze" and "Diamond Girl" in the 1970s.
Until Dan Seals got sick, the brothers were working as a duo, Seals & Seals. They performed some shows and were recording an album but never finished it. The songs they did complete, about eight in all, will be released.
"In the last two years he only did like three shows," Gottlieb said. "He just didn't have the energy."
Seals, whose father was a pipefitter, was born in McCamey, Texas, and grew up in Iraan, Texas, and Dallas.
His well-crafted songs tended to be insightful and graphic with lofty themes. In 1989, his music video for the song "Rage On" addressed a topic rare in country music: an interracial relationship. It showed angry youths smashing the windows of the car of a young man dating a girl of a different race. One boy hurled a beer bottle at the girl's father. The song itself was about small town values.
"When we record songs, we take chances," Seals said at the time. "We feel we are on the cutting edge of what we can do."
Associated Press Writer Joe Edwards contributed to this report.
Copyright 2009 The Associated Press.
Stephen Colbert and Mindy Kaling have collaborated together on quite a few made-for-TV movies. More specifically, made-for-this-TV-segment movies.
Supreme Court Justice Ruth Bader Ginsburg invited Stephen to Washington, D.C., to settle the case of "Do you even lift?"
'Santa Clarita Diet' star Drew Barrymore's 1995 'Late Show' appearance made a lasting impression on a lot of people. Not the least of which, David Letterman.
Crackle's 'The Oath' star Sean Bean left a markedly different impression on the 'Lord of the Rings' movie franchise than his acting counterparts.
'Black Panther' and '9-1-1' star Angela Bassett remembers the difficulty in shooting the dramatic fight scenes in Wakanda (AKA Atlanta).
'Tom v Time' star and 'The TB12 Method' author Tom Brady tells Stephen how to cope with losing a Super Bowl. (Not the Stephen will ever have to worry about that.)
Champion of the timesupnow.com movement Reese Witherspoon and U.S. Olympic medalist Adam Rippon combine talents to create the master class in 'Acting On Ice.'