This classic has never been a hit; check out the C&W top-40, you won't find it there. It did become Bill Monroe's most famous composition in the classic bluegrass line-up: Chubby Wise (fiddle), Howard Watts (bass), Lester Flatt (guitar) and Earl Scruggs (banjo). Monroe played it like a waltz in an attempt to capitalize on an earlier success with Kentucky Waltz. Again a waltz, that's in fact what irritated Elvis, reason why his 'rockabilly'-cover sounds like a pure parody.
Billy Swan [in the Sun studio]
John Fogerty [on Bill Monroe tribute]
Without an alert Sam Phillips, rock 'n roll might have been a footnote in music history and Blue Moon Of Kentucky forever a decent country waltz by Bill Monroe and nobody else. Rockabilly didn't even exist when Elvis started goofing around with this tune and without Sam's ad rem recording instincts, the momentum would have vanished in the haze, period.