It's sending sound parameter information (e.g. filter cutoff at 12khz, resonance at 1.6, Q of 0.89) along with note information (e.g. start playing note A4 with velocity 80). You could absolutely use a MIDI CC channel to convey this information. The OP-32 chooses a different route and encodes this into an audio signal so that it can transmit it over the air using the speaker/mic instead of a wireless stack.

I bet it sounds like a dial-up tone!