Why adding to library keeps adding into an additional "music" folder

a. The default layout of the Music media folder is <Media Folder>/Music/<Artist>/<Album>/[D-]## <Name>.<Ext> where <Media Folder> is the location set in preferences and <Artist> may be Compilations, <Album Artist>, <Artist>, or Unknown Artist. The extra Music folder is a legacy of iTunes Media Organization introduced back in iTunes 9 which moved artist folder from the root of the media folder into a Music subfolder such the media folder would be subdivided by media types. There is a hidden preference file in the media folder that can be tweaked to revert to the older layout. Open the file with a suitable text editor and change the integer value from 1 to 0, then turn keep organized... off and on again.

b. Try Repair security permissions for iTunes/Music for Mac - Apple Community.

tt2

With Musc closed open your media folder in Finder, press Shift+Cmd+. (period) to show/hide hidden files. Open .Media Preferences.plist with TextEdit or similar then edit this line:

<integer>1</integer>

to:

<integer>0</integer>

Save the change, start Music, turn Keep organized off, apply, then turn it back on again and apply to have any content in the nested /Music/Music folder pop up one level.

FWIW the standard location of the media folder in Catalina or later is ~/Music/Music/Media but presumably yours is set to ~/Music.

tt2

How odd. I would expect there to be a .Media Preferences.plist in any folder that has been selected as a media folder at any point. With Music closed can you copy the file you do have from one path to the other, make sure its integer value is 0, then see if running Music and turning Keep organized off and on again moves your artist folders up into iTunes Music?

tt2

You're not trying to make changes while using AirPlay are you?

tt2

What is your media folder as listed under Music > Preferences > Files?

Have you edited the hidden .Media Preferences.plist file in that folder?

tt2