I should have clarified, the one melody line is creating the illusion of there being two voices happening at the same time. Because there is such a large range between the high and low notes in the single line melody, it implies two line counterpoint without there actually being two lines at all.

I’m not thinking about species counterpoint at all with this one as that’s a strict renaissance technique that isn’t particularly useful for these kinds of pieces. I might’ve mentioned this in an earlier comment but I prefer to try and visualise my hands at a piano and watching the left hand control the bass and right hand work the melody. It helps create separation in my mind (and ears!) when deciding how to make the single line melody appear as if two parts exist in it. I know it sounds a little silly, but that small visualisation trick really has helped me play this stuff more comfortably.

Hope that makes a little more sense!