It’s July ninth, and on this day in 1954… riding the wave of excitement from the radio debut of “That’s All Right,” Elvis Presley returned to Sun Studio with Scotty Moore and Bill Black to record the B-side. The trio laid down their energetic take on Bill Monroe’s “Blue Moon of Kentucky,” transforming the bluegrass classic into a rocking companion to their first hit. This session completed Elvis’s debut single and cemented the raw, genre-blending sound that would help ignite the rock and roll revolution.