I'm sure you probably know this tune from the group they were in a couple years earlier:
"was originally conceived as a
bossa nova song played on guitars, but the other two members of the band,
Kevin Godley and
Lol Creme, were not impressed with the idea for the track and it was abandoned (...) Although taken aback by the suggestion, Stewart and the others agreed to try Godley's idea and create "a wall of sound" of vocals that would form the focal point of the record. (...) Stewart spent three weeks recording Gouldman, Godley and Creme singing "ahhh" 16 times for each note of the
chromatic scale, building up a "choir" of 48 voices for each note of the scale. The main problem facing the band was how to keep the vocal notes going for an infinite length of time, but Creme suggested that they could get around this issue by using
tape loops. Stewart created loops of about 12 feet in length by feeding the loop at one end through the tape heads of the stereo recorder in the studio, and at the other end through a capstan roller fixed to the top of a microphone stand, and tensioned the tape. By creating long loops the 'blip' caused by the splice in each tape loop could be drowned out by the rest of the backing track, providing that the splice in each loop did not coincide with any of the others. Having created twelve tape loops, one for each of the 12 notes of the chromatic scale, Stewart played each loop through a separate channel of the
mixing desk. This effectively turned the mixing desk into a musical instrument complete with all the notes of the chromatic scale, which the four members together then "played", fading up three or four channels at a time to create "chords" for the song's melody. Stewart had put tape across the bottom of each channel so that it was impossible to completely fade down the tracks for each note, resulting in the constant background of vocals heard throughout the song."