I make this node tree using "bake sound" mainly. I hope it helps, I have been investigating the possibilities offered by this node and some possibilities of use.
The first time we need to bake a sound, with these nodes it is possible to establish the number of frequency ranges, and the values that comprise them. In this case I choose 9 intervals, configured by default and bake the spectrum data. This may take several seconds
Later, insert evaluate. If we debug this node, we can view the array data of any of the frequency intervals:
To get all the frequency data, we will need to add a node (get list element) for each interval. In my case I used this node tree to move an icosphere around the blender space, this icosphere gets a paticle system who emits metaballs to shape this movement (and I modified the damping).
This gray node uses it as a converter, the float controls the proportion of the movement. Later, we combine the data in a vector.
To interact with the metaballs particle system (to add modifiers, etc etc.), we translate the mesh to another object.
To view the node tree results go to this video https://youtu.be/q1z6DxcDDIk thanks!! enjoy :)