On the errors, it looks like I used the wrong magical incantation to pull mesh data back from the void. It's fixed, and I've updated the node library on Github.
The goal is to create a list of 3D points from a list of amplitudes across all the audio frequencies and "map" these 3D points spatially (distributed around a sphere for example). Each 3D point placement and possibly individual shader values would be affected by its own amplitude data.
You could accomplish this by first mapping the frequencies to an image, then projecting that onto a mesh. Here's an example I made up (it uses a custom node Make Image From Pixels, available here).
