This is a blend file of a procedural setup, which instances an object every frame along a predefined curve. (Here the object is, for example, a Metaball).

This opens possibilities to scale those instances by any frame-by-frame value, like an audio input. Here, for fun, it is presented as an audioreactive setup. But the scaling value can be anything or driven by manual keyframes.

(The blend has detailed explanations)

This file is not part of a series of the demonstrations of the capabilities of Geometry Nodes. It utilizes Animation Nodes (Link included), because it has the functionality needed. The An has the capability to split the audio into spectrums and use a chosen band as a drive value.

Therefore you need AN installed for the Blend to work ! (Link - https://animation-nodes.com/)

(If you wish a pure GeoNodes setup, see the "Wire" or the "Curve scaler setup" !)

The nodes are set up, so all you need is change the settings as you wish and there you go ! (If you wish to dig in, the Animation Nodes is a visual script addon, just like Geometry Nodes and is extremely useful, specially when they are working together. Here the setup is simple and easy to read.)

All necessary files and links included in the content.