Thank you so much for the kind words :) it took me way too long to make the background but i am happy how it turned out :D
Its moving to the music audio spectrum from left side low frequencies and right side high frequencies + some other magic for smoother swings :D.
Volume is the height of the block and if you play around with music volume(not master) or mute in the options it is affected :D
But i didnt start the shader from zero, i started with converting this https://www.shadertoy.com/view/4sSBW3 to a godotshader and went on from there. still took me around 16 hours of research, coding and tinkering^^
The Graph is the Graph2D Node (https://godotengine.org/asset-library/asset/1784) with some adjustements by me