Ok! So I spent a lot of time refining this. I redid a bunch of chords, and I fussed with the patches a bunch - I made a much better sounding "organ", which has a good percussive start and sustain. I was having trouble with that one because if you just use the filter envelope, you can make the percussive hit but then you've faded out the instrument and you can't get it back, because it's a simple ADSR curve. But, I figured out you can use the LFO to bring the volume back up! I'm learning :)
I also worked out a really crunchy bass line, by using the LFO set on "Random 2" to control the duty cycle of the PWM oscillators... so you get a good feedback sort of sound. I promise all these acronyms mean things :)
Composition-wise... I expanded out the chords to add more depth, and I subtly doubled up the trumpet in a couple of parts. I made good use of suspended chords and augmented chords, which gives it a more dance-y sound in spots.
I like the TR-909 a lot, but I feel like its crash cymbals are a little weak. I tried subbing in some bigger ones, but they didn't really fit the synth sound, so I'm kinda stuck with them though. Oh well.
I think this is the final version, but I'm sure I'll still find something to fix :)