Johnny Cash’s 1956 classic “I Walk the Line” established him as a star with its unique sound and earnest lyrics. Cash’s deep voice, steady “boom-chicka-boom” rhythm, and humming between verses created a hypnotic effect. He wrote it as a pledge of fidelity, and its honesty paid off: it was a No. 1 country hit and crossed into the pop Top 20. Decades later, it remains Cash’s signature song and a cornerstone of country music history.