30 Copies

“It sold about 30 copies,” Martin recalled. Upset, Mathers returned with an alter ego: Slim Shady. FBT sold thousands of “The Slim Shady EP,” which eventually landed in the hands of mega-producer Dr. Dre.

While Dre receives most of the credit for turning Mathers into Eminem, the Bass brothers produced many early hits, including a dozen tracks off “The Slim Shady LP,” as well as “Lose Yourself,” the hit song from the biopic “8 Mile.”

“We really developed Marshall up until the time we brought him out to L.A.,” Martin said. “That’s when somebody heard him and got the tape to Dr. Dre.”

Earnings from the brothers’ Eminem holdings grew 43 percent to $5.07 million last year, according to Royalty Flow. The artist had sold more than 44.9 million albums as of 2014, according to Billboard magazine.

The proliferation of paid streaming has lifted the music industry after almost two decades of decline. A Goldman Sachs Group Inc. report recently predicted worldwide sales will exceed $40 billion by 2030, up from $15.7 billion on 2016.

Investor Interest

That optimism has produced a flurry of deals. BMG Rights Management GmbH acquired Nashville label BBR Music Group in January. In June, Imagem, which holds rights to 250,000 songs spanning Daft Punk, Pink Floyd and Stravinsky, sold in a deal Billboard pegged at $600 million. A couple weeks ago, Warner Music Group acquired Spinnin’ Records.

Investors will be able to buy as much as 80 percent of Royalty Flow, whose primary asset is future earnings from the brothers’ share of Eminem’s catalog. Though the rapper hasn’t released an album in a few years, he remains one of the most popular artists on streaming. More than 18 million people listen to his music every month on Spotify.

“We’re creating an avenue where we can cherry pick some of best assets in music business and provide an alternative asset for investors to participate in,” said Schneider, the chief financial officer.