From Wikipedia: "Floyd Cramer was one of the architects of the "Nashville Sound." He popularized the 'slip note' piano style where one note slides effortlessly into the next. This was a major departure from the percussive piano style which was popular in the late 1950s.
Cramer moved to Nashville in 1955 where the use of piano accompanists in country music was growing in popularity. By the next year he was, in his words "in day and night doing sessions." Before long, he was one of the busiest studio musicians in the industry, playing piano for stars such as Elvis Presley, Brenda Lee, Patsy Cline, The Browns, Jim Reeves, Eddy Arnold, Roy Orbison, Don Gibson, and the Everly Brothers, among others. It was Cramer's piano playing, for instance, on Presley's first national hit, "Heartbreak Hotel." However, Cramer remained strictly a session player, a virtual unknown to anyone outside the music industry.
Cramer had became well known following the release of "Last Date", a 45 rpm single in 1960. The instrumental piece exhibited a relatively new concept for piano playing known as the "slip note" style. The record went to Number two on the Billboard Hot 100 pop music chart, and sold over one million copies, and was awarded a gold disc."