When using echo on a magnetic tape came to mind it was done by cutting the tape to create a loop, using a reel to reel tape machine the sound would be recorded onto that tape and played back in real time while whomever was playing played. The time between the original sound and the echo was dependent on the length of the tape loop and the placement of the 'record' tape head and the 'play' tape head. The video is of Les Paul and Mary Ford's track from 1951
