Neopixel Strip controlled with sound

Okay, so I am wondering for a while and I am a littlebit clueless. I want to make a sound reactive neopixel led strip which does not use a microphone. Only my windows (more likely only spotify’s for exaple) sound data. My idea is the color changes based on the frequency of the music. (like higher frequency = colder colors, lower = warmer)

If anyone done something similar to this can you help me? (I don’t want a code or anything like that just a little where to start help) I am kind of a newbie so please do not attack me if it is a real easy question.

have a look that this example:

the part that probably would be different for you would be that you might need to build an amp circuit (in replacement for the microphone) to connect your arduino to your PC audio jack (to 'hear' your music)

if it frequency and NOT sound level your are after, that may be a tad more complicated! ;)

Consider a Teensy 3.2 and the PJRC Audio Library. It provides input objects for USB Audio and FFT objects for frequency analysis. There’s also a library that runs NeoPixel strips with one of the Teeny’s UARTs using DMA. That allows interrupts to remain enabled and not interfere with audio processing.

I did something similar using a Nano and an MSGEQ7 chip. Mine used a microphone but you could easily make it take an analog line in. I used the big individual through-hole WS2812 LEDs but they work just the same as neopixel strips.