Phillips, meanwhile, was always on the lookout for someone who could bring the sound of the black musicians on whom Sun focused to a broader audience. When he acquired a demo recording of Without You and was unable to identify the vocalist, she reminded him about the teenaged singer. She called Presley on June 26. However, Presley was not able to do justice to the song. Despite this, Phillips asked Presley to sing as many songs as he knew and, impressed enough by what he heard, he invited two local musicians, guitarist Winfield "Scotty" Moore and upright bass player Bill Black, to audition Presley. Though they were not greatly impressed, they asked him to attend a studio session the following evening. Presley transformed not only the sound but the emotion of the song, turning what had been written as a "lament for a lost love into a satisfied declaration of independence."
The session proved almost entirely unfruitful, but late in the evening, as they were about give up and go home, Presley launched into a 1946 blues number, all of a sudden, Elvis just started singing That's All Right, jumping around and acting the fool, and then Bill picked up his bass, and he started acting the fool, too. Phillips quickly began taping; this was the sound he had been looking for. Three days later, popular Memphis DJ Dewey Phillips played That's All Right on his Red, Hot, and Blue show. Listeners began phoning in, eager to find out who the singer was. The interest was such that Phillips played the record repeatedly during the last two hours of his show. Interviewing Presley on-air, Phillips asked him what high school he attended in order to clarify his colour for the many callers who had assumed he was black. 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 "slapback". A single was pressed with That's All Right on the A side and Blue Moon of Kentucky on the flip.