Ashford & Simpson - Bourgie Bourgie. one of my definite disco favourites. No synths whatsoever plus huge strings and brass, features that would normally scare me the hell away from a tune. Not this time, though. Absolute class.
A less polished version by John Davis & The Monster Orchestra. A beauty, nonetheless. And with vocals to boot!
And here's a short live version of Bourgie Bourgie by Gladys Knight & The Pips: