Can Music Library be stored on an external HD?

Clicking on a library file opens the application, but not necessarily with the selected file. You must use the option-start-Music method, then choose a library. The default location for a Music library is ~/Music/Music where ~ is your user's home folder. Move this folder (the nested Music folder) to a new location, then option-start-Music to select the Music Library.musiclibrary inside. The default location for media in a new Music library is ~/Music/Music/Media (which would travel with the Music folder), but if your library has been converted from iTunes then the media may well be in ~/Music/iTunes/iTunes Media. This folder should not be moved by hand. Instead after opening the library in the new location use Music > Preferences > Files to reset the media folder such that it is <NewLocation>/Music/Media then use File > Library > Organize Library > Consolidate Files to bring in copies of the original files. Removing the originals is a manual task once you're happy the library is working correctly in the new location.

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Yes, you can move the library to an external drive. You can move the entire ~/Music/Music folder, then press and hold down option as you launch Music and use the choose option to select the library in the new location. You open the Music Library.musiclibrary file inside the relocated folder.

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