How to disable or uninstall iTunes under High Sierra without disabling SIP
I wasn't able to find a list of all the file types iTunes handles, but if you are willing to operate piecemeal, any time you open a file and iTunes launches, you can


Select the file in Finder
Get Info (⌘ + i)
select the app you want to use in the "Open With:" dropdown


then click "Change All..."


In the future that type of file will open in your alternate application. After a while you will have opened all the types of files you will open that iTunes handles.

Another method that you may find easier:


Right Click (or control click) the offending file in Finder
Select "Open With > Other..." (even if you see the app you want to use in the list)





Select your App (e.g. Audacity)
Check "Always Open With"

Click "Open"


It just depends on which way you find easier.