Static? Ofc I don't mean static. I mean evolving. You can do all sorts of modulation on the synth itself (and in this case on effects and volume on specific layers of the printed synth). For that you can use any (and multiple) MIDI CC.

 

Before tracking the synth, you can program much more than just filter to dynanic (what in midi language is called velocity), of course it means that you have to know how to play using velocity, or edit manually after, which depending of the complexity of the synth part can be easy or a pain.
These are some parameters that could be assigned to velocity and create a lot of expression:

- Modulate your main(s) Oscillator(s) with a bit of FM, assign the quantity of FM mod to velocity.
- Using 2 or more oscillators, consider one or more as your core sound, and another one or more as your expression complement, assign the volume of this second osc to velocity.
- Use an adsr envelope on both a second filter band pass and a 2nd osc attack and sustain, assign the envelope to velocity.
- Assign distortion to velocity.

I could go on, but I suppose you got the trick the first trick, and any other direct modulation to the main oscillator's wave form is going to really give a lot of expression.