Elvis Presley was a huge fan of The Statesmen Quartet. He saw them sing when he was a child and idolized them to a degree. On at least one occasion, The Statesmen Quartet let him sing with them in the place of Jake Hess for a song or two.
Elvis went on to be a huge star in his own right. But, he got his style from The Statesmen Quartet. His leg shaking came from Jim "Big Chief" Wetherington, the bass for the Statesmen. Elvis patterned his vocal style after Jake Hess, the Statesmen's lead singer, who is said to be his favorite singer.
How Great Thou Art
When Elvis died in August of 1977 (just two days before my twelfth birthday), Jake was asked to sing at his funeral. He sang "Known Only to Him." The following video is Elvis' rendition of the song. Here is a link to The Statesmen Quartet singing the song as well: Known Only to Him.
Known Only to Him
Wikipedia - The Statesmen Quartet
Wikipedia - Elvis Presley