The song was "That's Alright," and the composer was Arthur Crudup. As a Black performer in the 40s and 50s, he was cheated out of millions of dollars in royalties by his manager. But without him, Elvis may never have been discovered. 

"By 14, he was working in a foundry...In Chicago, seeking a better job, he busked and slept in a crate under an L station. One evening on a street corner, Crudup met Lester Melrose, a white field agent for Bluebird Records.

“He put a dollar in my hand and asked me to play,” Crudup told High Fidelity magazine.

Arguments abound over who wrote the first rock ‘n’ roll song. But “That’s All Right,” mixing elements of blues and country, stakes a strong claim." 

Arthur Crudup wrote the song that became Elvis’ first hit. He barely got paid