Sorry, I can't write the manual right now. The program is well structured.
Understand one of the music procedures, such as void zmu1(). The subroutine has only 20 lines of code. Change it yourself and check the result.
zmu1()-zmu10() is a musical program.
subXX () is a dynamic program.
In readData[i] are the values of the band-pass filters.
readData[0] - output of the lowest frequency output.
readData[19] - output of the highest frequency output.
Process them according to your algorithm to get beautiful programs.
All the best for you.

Up to 240 (divided by 20 without residue), the LEDs can be entered sequentially. In the sketch change the #define stripled = 120 to the number of LEDs in your strip. For example: #define stripled = 240.
You can also include several LED stripes in parallel. In the case of parallel connection, transfer the control signal from the D2 output to the required number of LED strips.
Do not exceed the permissible output load of D2.
Do not exceed the power rating of your power source.

Has added the English version of the program.
https://github.com/juraspb/MusicToColor/tree/MusicToColor7