How do I make music pack

I know there a toturial video on YouTube but I think it's outdated so please help me

In order to make a music pack, you'll need a lump editor (such as Slade or XWE) and some music, preferably in .ogg format. You'll need to put the music in the lump editor and rename it to the music you want to replace. For example, if I wanted to replace Pipe Tower's underground music, I'd rename the new file to O_MARIO2.ogg and then import it into a new wad.

Following what NAR said, here’s the link to the wiki with all the specifics of making a Music Pack/ adding custom music or sounds to your mods. If you want to know the exact names of each song you wanna replace, with the Lump Editor, open up Music.dta from the SRB2 root folder and from there you can see the name of and listen to each song and sound effect that is in the game.