"I Feel Love" by Donna Summer (1977).
The backing track was written by Giorgio Moroder and was, as far as I recall (and I am old enough!
) the very first pop song to use nothing other than a synthesiser as a backing track. Bearing in mind that this was at the very beginning of the disco era, it was quite something!
Edit: Damn, KoS, you beat me to it... but then you would!
