The years at Sun Records, from 1955 to 1958, established Cash as a significant figure in what was then being called rockabilly — the collision of country music with the rhythm and energy of rhythm and blues. His label mates at Sun included Elvis Presley, Jerry Lee Lewis, Roy Orbison, and Carl Perkins, whose “Blue Suede Shoes” had been one of the defining early rock and roll records.
Cash was part of this moment but also slightly apart from it. Where Lewis and Presley performed with an almost theatrical frenzy, Cash performed with stillness. Where their music was about transgression as excitement, his music was often about transgression as consequence. The songs he wrote and chose to record in this period — about trains, about prisons, about men on the wrong side of the law — were not celebrations of lawlessness but meditations on what it felt like to be trapped, whether by poverty or circumstance or the choices you had made.
“I Walk the Line,” recorded in 1956, reached number one on the country charts and crossed over to the pop charts. It became his signature song, a declaration of fidelity that was also, in its structure, a demonstration of discipline: the song modulates key with each verse, requiring the singer to shift his vocal register accordingly. Cash moved through the keys without flourish, another example of technical difficulty made to look effortless.
By 1958 he had become the first Sun artist to release a full-length album. He had also grown restless under the Sun contract, which limited him in ways that larger labels would not. He moved to Columbia Records, where he would spend the next thirty years, and where the trajectory of his career would eventually bottom out before it recovered.