Les Paul was one of the first musicians to use sound-on-sound recording techniques, which paved the way for today's multi-track recording concepts. He began expermenting with it in 1948. He is also the first person to use studio technology to speed up and slow down guitar phrases by changing the playback speed of the recording. Patti Page was the only other artist to record sound-on-sound around the same time. It appears, they both came up with their own independent methods of achieving sound-on-sound recording, but it was Les Paul's technique that caught on and led to the multi-track recording industry.
Guitar 
