Consolidating Apple Music and my own library?

Changing the media folder location affects where new or consolidated content will be put. It doesn't change the location of the .musiclibrary file, so if this is currently on the external drive you should copy it over and option-start-Music to connect to it on the new path. Once you've consolidated the whole library to the new path on the internal drive you would be able to disconnect the external drive. All your playlists, ratings, playcounts, etc. will be preserved. I would recommend you clone the resulting Music folder complete with the .musiclibrary file and the Media folder back to this external drive or another for security.

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Leave the Apple Music content in its own folder. This is content that will no longer work as and when you choose to terminate your Apple Music subscription and in some cases you might need to do a manual clean up so best if it is all in one place. You cannot import Apple Music items into a library, they must be downloaded by Apple Music which will always put them in this custom folder.

When you're ready to consolidate to the new SSD you can reset the path to your media folder using Music > Preferences > Files. The standard location is ~/Music/Music/Media where your active library file is ~/Music/Music/Music Library.musiclibrary and ~ is your user's home folder. If you've moved the library elsewhere the reset option will put the Media folder in the same location as the .musiclibrary file, which is best practice. After consolidating with File > Library > Organize Library > Consolidate Files the library should no longer be dependent on the external drive. Apple Music content will still be in a separate folder.

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