The Time Lag Accumulator
The Time Lag Accumulator is a musical system that messes with time. Every note you play is repeated over and over every few seconds, until it gradually fades out. This means you can play a duet with the you from the past.
The Time Lag Accumulator was originally a system made out of two reel-to-reel tape recorders. You would record your music on recorder A, then play it back immediately on recorder B, feeding the output of B back to A.
The length of the resulting live loop was controlled by adjusting the physical distance between the two tape machines.
Pauline Oliveros used the Time Lag Accumulator in her work I of IV in 1966.
Terry Riley used it in Poppy Nogood and the Phantom Band , released in 1969. It is he who came up with the name "Time Lag Accumulation".
Brian Eno and Robert Fripp used the system on their (No Pussyfooting) record in 1972-73. This version of the system came to be known as "Frippertronics" . Eno also used the same system on Discreet Music , one of his early ambient works, in 1975.