“He had a kind of aura about him,” Mr. Blackwell, now 80, recalled in a recent interview. “I had an idea that he could have an impact.”

But Mr. Blackwell said he did not imagine the kind of pop-culture sainthood that Marley would ultimately achieve: tens of millions of albums sold, instant name-and-dreadlock recognition around the world, and an estate that, in Forbes’s estimate, earned $23 million last year, partly from the sale of family-branded products like speakers, coffee and Marley Natural cannabis.

While the family of Marley, who died in 1981 at 36, handles most aspects of his estate, Mr. Blackwell controls the rights to Marley’s music publishing catalog, including the copyrights to classic reggae songs like “One Love” and “Three Little Birds.” On Saturday Mr. Blackwell signed a $50 million deal with Primary Wave Music Publishing, a boutique New York music company, the latest in a string of high-profile transactions reflecting how streaming has boosted the value of music catalogs.

“Basic publishing is absolutely important, but it’s not very exciting,” said Mr. Blackwell, who speaks in a slow, soft British accent but carries two cellphones that chirp constantly. “But now it is the music business. Record companies used to manufacture, and that was the difference between a record company and a publishing company. All that is really gone now.”

Primary Wave has carved out a lucrative niche in music publishing by focusing on aggressive branding and marketing campaigns for what its founder, Larry Mestel, calls “the icons and legends business.” The company has a relatively small catalog of about 12,000 songs — its roster includes Smokey Robinson, Def Leppard and Steve Cropper, who wrote “(Sittin’ On) The Dock of the Bay” with Otis Redding — but promotes them heavily through commercial tie-ins, movies and TV shows.

Mr. Mestel, whose first job was working for Mr. Blackwell at Island, declined to offer any specifics about his plans for the Marley songbook. But as examples of his company’s approach he cited two past campaigns. When it managed Kurt Cobain’s catalog, Primary Wave did a deal with Converse to drape sneakers in Nirvana lyrics; for Aerosmith, it helped create a state lottery game, with each scratch-off card revealing words from Aerosmith songs.

For the estate of the pianist Glenn Gould, another client, Primary Wave plans to send a hologram of Gould — who died in 1982 and famously hated playing live — on a concert tour.

“There are a lot of inbound calls that music publishers get, where they hang up the phone and give each other a high-five, saying, ‘We just did a great job in marketing,’” Mr. Mestel said. “That’s not marketing. We’ve got almost 100 people that all they do is marketing, all day long.”

The Marley catalog is unusual. During his lifetime, he had few chart hits, but his music has achieved steady, far-reaching popularity that has lasted for decades. According to Nielsen, his songs has been streamed more than 1.7 billion times in the United States alone, and Marley’s fame permeates deep into emerging markets like Africa and India.

“There isn’t a crevice of the world,” Mr. Mestel said, “where Bob Marley isn’t a god.”

Unlike most publishers, Primary Wave sees itself as a branding house and an asset manager, exploiting song catalogs on behalf of investors that have contributed to an acquisition fund. Primary Wave has about $400 million to invest in music on behalf of those investors, who include BlackRock, Mr. Mestel said.

 

Over the last year, hundreds of millions of dollars have changed hands in music-publishing transactions. In June, Concord paid almost $600 million for Imagem, which includes the Rodgers & Hammerstein catalog. In December, Kobalt bought Songs (Lorde, the Weeknd) for $160 million, and thist week Round Hill Music closed a $240 million deal for Carlin Music, which includes standards like “Fever.”

Money managers, lawyers and music executives say that a confluence of factors, including low interest rates and a roaring stock market, has created an especially frothy market for alternative investments like music rights. And the success of streaming has quickly given a boost to catalog valuations, pointing to the possibility of steady growing returns for years to come.

“We’re experiencing growth from multiple sources simultaneously,” said Barry M. Massarsky, an economist who specializes in valuing music catalogs. “It’s a perfect storm of value for music publishing assets.”

In a competitive market, Primary Wave’s pitch to songwriters is finding ways to market old material. For Mr. Robinson, who signed a $22 million deal with Primary Wave in 2016, the company did a deal with American Greetings to promote a new holiday, Father-Daughter Day, using Mr. Robinson’s song “My Girl.” When he was looking for a new home for his songs, Mr. Robinson said in an interview, those ideas sold him.

“When I got to Primary Wave, they had made up a brochure with all kinds of things to show me how they operate,” Mr. Robinson said. “It had my picture on the cover and my songs listed and everything. It was just so attractive to me, I signed with them.”

Mr. Mestel said that he seeks only tasteful deals. But the Marley family controls the use of their patriarch’s name and likeness, and Mr. Blackwell said that the family, which earns the majority of the songwriting royalties, has the final right to refuse any use.

Mr. Blackwell, who began his career selling Jamaican singles out of the trunk of his Mini Cooper in London, built Island into a major power with Marley, Stevie Winwood, Cat Stevens, Grace Jones and U2. In recent years, he said, he has devoted himself to his Island Outpost collection of resorts and Blackwell Rum, downsizing his music publishing business to just a few employees.

But the new partnership with Primary Wave, Mr. Blackwell said, had him excited about returning to music, and to the worldwide popularity of Marley.

“I was in Singapore last year in a little bar,” he said. “Suddenly you look up, and there on the TV, singing a song, is Bob Marley.”