Reverse-engineering my speakers' API to get reasonable volume control

I love this type of posts, and I’m amazed the speaker exposes its API like this.

The kid in me thinks there could also be a way perhaps to transmit audio through this (or another) API? (very low chance, but…)

From his filesystem listing in the post it looks like you can overwrite firmware update data. I wouldn't be surprised if you can make it play or capture whatever you want be overwriting the firmware.