As part of the outdoor installation Pop-Up-Sound-Garden, I wanted to put a speaker inside a massiv concrete drain pipe.
I found an unused flower pot that happened to fit the speaker element I had at hand perfectly, and inside the pot there was enough room to add electronics. So this flower pot now runs on 12V and contains a Raspberry Pi Zero W with a USB sound card, a DC-DC converter, and a 3W amplifier. On the Rpi I installed piCore Linux and SuperCollider.
The music that SuperCollider is generating is based on tweet0406 with some added bass notes. It all sounds pretty good and loud for such a small mono speaker setup.
Finally, I attached a distance sensor so that the synthetic sounds only start playing when someone passes by or stands in front of the speaker.