I think that Elvis (besides the fact that he was indeed way cool

) broke at least some of the bounderies in music just by becomming famous.
He just loved music, but not just Black OR white, he liked Dean Martin and Sinatra, Hank Williams, Muddy Waters and probably his biggest idol Big boy Crudup.
many people did the same thing, even Robert Johnson sang cowby songs. But Elvis made it clear to the rest of the world that in music there are no bounderies.
However the reason for his succes was his talent, his voice and charisma. The most innovative thing he's ever done was just being Elvis.
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TstikeB