Jerry Lawson (Stacie Huckeba/AP)

Jerry Lawson, who for four decades was the lead singer of the eclectic cult-favorite a cappella group the Persuasions, died July 10 at a hospice center in Phoenix. He was 75.

His friend Rip Rense confirmed the death but did not disclose the cause.

Mr. Lawson’s smooth baritone led the group of five and later six singers, who were revered as “the Kings of a Cappella” by their small but devoted fan base.

Through 25 albums, the Persuasions recorded rock, blues, gospel and pop songs, all with no sound other than their own voices, long after the doo-wop era and long before the “Pitch Perfect” movies, when a cappella was rare.

They began as a casual and nameless collection of singers on the basketball courts and front stoops of Brooklyn in 1962, with Mr. Lawson bringing the warm, friendly voice he developed singing gospel songs during his youth in Apopka, Fla.

“It was just five guys who used to stand on the corner or go down to the subway station every night and just do this,” Persuasions member Jimmy Hayes told the Associated Press in 2000. (Joseph Russell, Herbert Rhoad and Jayotis Washington rounded out the original quintet.)

Jerry Lawson (Pat Johnson/AP)

Musician Frank Zappa gave their career a boost when he discovered them in the late 1960s and signed them to his independent label for their first album in 1969.

The Persuasions performed with everyone from Liza Minnelli to Joni Mitchell to the Seattle Symphony Orchestra and covered the songs of Motown, Sam Cooke and Paul Simon.

The eclecticism that made them so beloved also kept them from reaching pop stardom. Music executives never knew how to market them, and commercial radio had no clue what niche to stick them in.

Jerome Lawson was born in Fort Lauderdale, Fla., on Jan. 23, 1944, and grew up in Apopka. Survivors include his wife.

Mr. Lawson left the group in 2002. A few years later, he joined a much younger group of San Francisco a cappella singers that had based themselves on the Persuasions to form “Jerry Lawson and the Talk of the Town.”

The group released an album, co-produced by Mr. Lawson and his wife, Julie, in 2007, and a few years later, they appeared on NBC’s music competition show, “The Sing-Off.” In 2015, he released his only solo album, “Just a Mortal Man.”