The first “disco” song was the theme from the movie Shaft. Right on.
....”can you dig it?”
There’s a lot of discussion on which was the first. And it’s basically impossible to tell since really it’s funk with one instrument laying down a pedestrian beat. Given that Isaac hung out in both worlds I certainly wouldn’t discount Shaft from possible candidates.
I used to have the usual rocker party line on disco, but as I started getting into funk I had to change. Especially once you get to the late 70s, the line between the two is so thin at that point as to be basically non-existent.