Track one has a kick dum.
Track two has a polyphonic saw wave synth.

The level of track two is modulated (negative) by the level of track one.
An envelope follower is used to convert the track one audio level into a control signal used in the AMP module of track two.

Note: The “T1 Env Follow” knob at the end of track 2 lets you adjust the pumping amount in both positive and negative directions.

Remember that by tap-moving your finger horizontally on a knob, you can fine-adjust its value, and by double-tapping, you can reset its value or enter a number manually.