Behind the Groove gives all the details you need to know about the recording of this 10cc classic.
The trio spend three weeks recording the vocal phrase “ahhhh” sixteen times for each note of the chromatic scale, building up a choir of 256 voices that are spread across a sixteen track multi-track tape. Wanting the voices to repeat in perpetuity, they create several tape loops each twelve feet in length. Having made numerous tape to tape bounces of the choir section results in an audible degradation of the vocals, creating the eerie, soft sound that is one of the songs hallmarks.
Fascinating.
