The code can be found here. To upload it, you will need the NeoPixelBus library. You can download it here or using library manager, search for "NeoPixelBus ...
Inspired by https://robtrevino.com/2019/06/23/using-a-rgb-led-strip-as-an-audio-visualizer/. I took his code and made my own version of it, it is not perfect but it ...