AudioLink lets you change how your avatar looks using the audio played in specific VRChat worlds.
This tutorial explains how to add AudioLink to your avatar using the popular Poiyomi Shader.
Tested with Poiyomi Shader v8 however the steps are identical for v7. Tested with Unity 2019.4.31f1, VRCSDK3-AVATAR-2022.04.21.03.29_Public and the Canis Woof by Rezillo Ryker.
Download and install the latest Audio Link Unity plugin (minimal). It will let you test Audio Link inside Unity.
In your Unity scene drag the prefab at Assets/AudioLink/AudioLinkAvatar.prefab to anywhere in your scene (but do not put it inside your avatar).
To test Audio Link we need a suitable audio clip. Try your favourite MP3 song that has a good range of treble and bass. Add it to the audio source in your scene under AudioLinkAvatar/AudioLinkInput.
In your avatar find the material that you want to enable Audio Link for. Open the Poiyomi shader settings and enable Audio Link.
In this tutorial we will make your avatar "glow" when a song is playing. Enable an emission and set the colour and mask. Set strength to 0 (it will be turned on by Audio Link later).
Check the "Audio Link" box. It will show you options to configure Audio Link. Under Emission Strength set Y to 1. Under Emission Add Band select treble or bass.
X means when there is no audio. Y means when there is audio. Set a value to inbetween 0 and 1 to have it at half volume, etc.
Treble is the highest point of music (usually the singing or guitar or whatever). Bass is the lowest point of music (usually the beat).
Click Play. Your song will immediately start playing and your avatar should start lighting up! Audio Link is now ready for when you play VRChat.
You can visit this world in VRChat to test it in-game.