The A-side of the album is a thirty-minute piece originally intended as a background drone for guitarist Robert Fripp to play over in a series of concerts. Eno set up a synthesiser with built-in memory along with a tape delay system, but was immediately interrupted: "people started knocking on the door, and I was answering the phone and adjusting all this stuff as it ran. I almost made that without listening to it. It was really automatic music".
It begins with two melodic phrases of different lengths played back from a synthesiser's digital recall system. This signal is then run through a graphic equaliser to occasionally change its timbre. It is then run through an echo unit before being recorded onto a tape machine The tape runs to the take-up reel of a second machine, and the output of that machine is fed back into the first tape machine which records the overlapped signals. The next day, Fripp visited and Eno accidentally played the piece back at half-speed, thinking that "it was probably one of the best things I’d ever done and I didn’t even realise I was doing it at the time."
The second half of the album consists of three related pieces, collectively titled "Three Variations on the Canon in D Major by Johann Pachelbel", performed by the Cockpit Ensemble. Eno described the music as the result of a self-generating, self-regulating system, with the input to the system taking the form of two- or four-measure fragments of Pachelbel's canon, and the system being the performers with a set of instructions.
Each variation involves a different way of manipulating and overlaying the musical fragments.
In the first piece, "Fullness Of Wind", the players' tempos are decreased, with the rate of decrease being related to the relative pitch of the instruments, so that lower instruments are slowest.
In the second piece, "French Catalogues", groups of notes are associated with time-related directions from different parts of the score.
The third piece, "Brutal Ardour", presents the players with sequences of notes that are related but of different lengths.
Rock and Roll, yeah!
Crikey, just looked and realised I've got this, don't think I've ever played it, must have seemed a good idea at the time.