So I’m recreating Geometry Dash currently (I said this for the third time lol) and I tried to recreate stereo madness. And I finished Stereo Madness (song only).
And I found out you can make songs in Desmos!
So the tone function helped me a lot. And C4 is 261.626 hz, every note is the previous’ 2^(1/12). And based on that, I made a function:
f(x)=261.626(2^(1/12))^x and f(0) is C4 and f(1) is C#4!
And if you want to see Stereo Madness in Desmos.
Open the Desmos link below and open folder: Music Engine and play the Hzitem and remember to unmute 
Here’s a tip- A4 is exactly 440, so if you use it as reference (just add 3 to the input) then the notes will be perfectly in tune!
Oh nice 
thanks for the tip