Maybe not strictly disco, but....
I am desperately looking for a song that I heard on the radio while on a Florida road trip recently. It was on an R&B station that played new and old-school stuff, so I can't really date the song. It had an old school beat, and I think it had two different male vocalist.

Here is the key: They were purposefully mumbling throughout the song. The melody of the verses was in a descending pattern. "Num num num num da na num da na num", starting with a higher note and descending to a lower note.

It was actually very catchy and could serve as a great dance tune. Any ideas? Thanks!