Volcanic Casting and Forge

Going over the video and extrapolated 3d models again, some of the technical designs are quite simple.

The primary reference (sphere, etc) use a very simple fabrication method:

Cast a sphere of obsidian or other material, confirm its structural integrity under pressure (or cast as vacuum or cast as high pressure air, etc) then drop it into a tone-locked vertical pipe with a hot plug (similar to how one would tune a barometer) and let it find its normal pressure where it matches the environmental resonance of the system and solidify with normal cooling.

The result, is a cute little pressurized ball that makes a perfect tone to any matched medium at a perfect harmonic of the control resonance frequency. It's natural selection of buoyancy based on the frequency of its natural resonance when matched with the environment tone gives a perfectly matched resonator with a glass plug. I'm sure you could do this with a cork or wax/pitch/tar on a wood diaphragm as well.