I remember Les Paul doing a live tv show where he had this little box strapped to his belt, he played something on his guitar, re-wound the tape played again, he did this many times, in the end he had about eight guitars or more, his own invention!
Here's the link to the book, well worth the money

and it was the writers who did the talk when I visited Abbey Road.
http://www.recordingthebeatles.com/Phil