This session, held on the evening of July 5, 1954, proved entirely unfruitful until late in the night. As they were about to give up and go home, Presley took his guitar and launched into a 1946 blues number, Arthur Crudup's "That's All Right". Moore recalled,All of a sudden, Elvis just started singing this song, jumping around and acting the fool and then Bill picked up his bass and he started acting the fool too, and I started playing with them. Sam, I think, had the door to the control booth open...he stuck his head out and said, "What are you doing?" And we said, "We don't know." "Well, back up," he said, "try to find a place to start and do it again." Phillips quickly began taping as this was the sound he had been looking for.During the next few days, the trio recorded a bluegrass number, Bill Monroe's "Blue Moon of Kentucky", again in a distinctive style and employing a jury-rigged echo effect that Sam Phillips dubbed to be "slapback". A single was pressed with "That's All Right" on the A side and "Blue Moon of Kentucky" as the B-side.