A pure GeoNodes setup of a frame-by-frame curve scaler, here driven by audio. Your curve radius is scaled by a current custom value, every frame, creating an evolving and reactive shape.

The setup also serves as an example of curve and spline handling in Geometry Nodes. You can realize your own vision.

Video demo and here, here, here, and here. Emitter version here.

A user-defined curve is scaled frame-by-frame. The curve radius itself is actuated every frame by the current value, be it audio or keyframe. 

There are two versions of the setup presented here, as example of various settings and styles. A special version with swirling particles emitting from the current height of the curve is added. 

There is an other setup with a similar effect available, where instead of scaling a curve radius frame-by-frame, we instance a standalone custom object and scale it by any current value. 

NOTES

-(Since it is a concept demonstration, it is kept as simple as possible.) The GeoNodes trees are kept clean, the nodes are not contracted into nodegroups for easier readability and have detailed explanations.)

-(This setup comes in two versions. One is the main version. The seconf one is a special addition, where a particle emitter follows the created curve to create a swirl of particles. )

-The file is optimized for and rendered in Eevee (Render Viewport animation). Of course, you can set up any renderer you wish.

--Follow the instructions in the description to change the setup and fine tune it to your audio ! (You need to bake it to an Fcurve, fine tune it trough the Map Range nodes, and add keyframes to the material to control the emission glow and colors as you wish)

Enjoy and blend like the wind !

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NOTE

-(Since it is a concept demonstration, it is kept as simple as possible.) The GeoNodes trees are kept clean for easier readability and have detailed explanations. Everything is built from the base. The point of these setups is to provide a base core of the concept, node from node, instead of contracting all into node groups with exposed settings, which makes everything harder to read and dissect.

You can embellish, refine as you wish based on the core or realize your own ideas.

-Read the text description, it has a lot of useful info !