From an Ernie site:

"In September, reeling from a demanding road and television production schedule, Ernie was informed by Capitol that he was approaching breach of contract. He needed to record two sides for a single release immediately. Armed with a box of fan mail, Cliffie Stone convinced Capitol head Lee Gillette to allow Ernie to record "Sixteen Tons", and Gillette agreed; it would be the B side of a country-blues swinger titled "You Don't Have To Be A Baby To Cry", a tune that Gillette and others at the label believed would be Ernie's biggest hit yet. On September 17, 1955, both songs are recorded at Capitol's Melrose Avenue Studios in Hollywood. To kick off the tempo for arranger Jack Fascinato, Ernie began snapping his fingers...mistakenly left on the master tape by Gillette and the engineers."

Spaw