McDaniels, whose career included many years as both a songwriter and a record producer, died Friday at his home in Kittery Point, Maine, after a short illness, said his wife, Karen.
McCann hired McDaniels as the first singer in his band in Los Angeles in the late 1950s.
"I couldn't believe we had someone that good, that young, in our band," McCann said. "We were all young and being creative and developing our talents. Someone picked him out and said, 'Let's make you a star.' "
After signing with Liberty Records, McDaniels scored his first major hit in 1961 with "A Hundred Pounds of Clay," which reached No. 3 on the Billboard chart.
Liberty reportedly wasn't quite prepared for the single's immediate success and did not release publicity photos of McDaniels for about six months. Many fans initially had no idea he was black until they saw him performing on stage.
"People were amazed. That really tickled me," McDaniels recalled in a 1994 interview with the Los Angeles Sentinel. At the time of the record's release, he said, having throngs of teenage white girls swooning over a black singer would not have been tolerated.
"If I had been white, I could have been a matinee idol," he said. "But being black, that was taboo."
McDaniels' other '60s hits included "Tower of Strength," "Chip Chip," "Point of No Return" and "Spanish Lace."
By the late '60s, McDaniels' pop stardom had diminished, but by then he was carving out a reputation as a songwriter.
McCann had a big hit with the McDaniels-written "Compared to What," a song on McCann and Eddie Harris' 1969 album "Swiss Movement."
McCann had recorded the song, an up-tempo social commentary, a few years earlier, but it had made no impact. Not so the second time around.
"When it was really a hit, we'd walk on stage, and they'd yell out 'Compared to What!' One night I said, 'Let's see if we can get by not playing it,' and we got booed. It's an amazing song. I do that song at least twice a night, and I still love it. All of his songs were fantastic."
"Compared to What" has shown up in eight movies, including "Casino," and was featured in an international Coca-Cola campaign. More recently, it was included on the 2010 John Legend and the Roots album "Wake Up!"
In the early '70s, Atlantic Records released McDaniels' albums "Outlaw" and "Headless Heroes of the Apocalypse," for which he wrote or co-wrote the songs.
"They were very political albums, and they got him kicked off his label," his wife said.
Flack's 1974 recording of McDaniels' "Feel Like Makin' Love" reached No. 1 on the Billboard chart and was nominated for two Grammys. McDaniels wrote many songs for Flack.
McDaniels' songs have been recorded by singers including Aretha Franklin, Nancy Wilson, Donny Hathaway, Gladys Knight & the Pips, Johnny Mathis and Ray Charles. He also produced for artists, including Flack, Knight, Lenny Williams and Melba Moore.
The son of a minister, Eugene B. McDaniels was born Feb. 12, 1935, in Kansas City, Kan., and grew up in Omaha, where he began singing in his father's church as a young boy.
He formed a gospel quartet in junior high school and, while idolizing jazz singers, including Billy Eckstine and Sarah Vaughan, launched his career after graduating from high school.
Karen McDaniels said her husband recently had been working on a new CD, "Humans Being."
Retirement wasn't on his agenda.
"Never," she said. "He couldn't retire because he was always writing music. Everything was about the music, always. It was his soul, his essence completely."
In addition to Karen, his third wife, McDaniels is survived by his sons, London, Christopher, Mateo, Django and Dylan; his daughter, Dali; his sister, Pat Nichols; and nine grandchildren.