Q: Use external hard drive for my music source

Quit iTunes. Find your iTunes folder in your user folder and copy it to your external hard drive. Restart iTunes while holding the "Option" key. Navigate to your iTunes folder on your external hard drive and select it. iTunes should now use this folder for your music.

Make sure it works before removing the old iTunes folder.

Another method:  Copy the iTunes folder to the new location, in iTunes go to Preferences > Advanced and Change the "iTunes Media folder location."

RogerOut wrote:

 

Another method:  Copy the iTunes folder to the new location, in iTunes go to Preferences > Advanced and Change the "iTunes Media folder location."

That won't work. You have to either move the entire library as indicated in a previous post, or use iTunes to relocate media only to  different drive. Changing preferences settings only tells iTunes to start putting any new media in that location, it won't get it to look for old media there.

Actually, it does work, if you know what you're doing...

Actually, to use this method...

(1) Create new iTunes Media folder on external drive (and leave it empty).

(2) In iTunes preferences Advanced tab, point to new iTunes Media folder location.

(3) Then, from iTunes menu bar

File -> Library -> Organize Library...  (with Consolidate files checkbox)

This tells iTunes to copy ("consolidate") its media files from their current locations, to the designated iTunes Media folder, organized into sub-folders by media type, artist, and album.  By telling iTunes to do the copying, iTunes keeps track of its media files.  If you copy the iTunes Media folder using Finder, iTunes does not know and loses track of media files.

(4) After confirming iTunes is accessing its media files from external drive, delete iTunes Media folder (in your iTunes folder) on internal drive, and empty the Trash to free up that space.

If by "know what you are doing" you mean consolidate (KenichiW's instructions) which I meant when I said "use iTunes to relocate media", but your instructions were incomplete.  Simply copying the media folder and changing media folder location in preferences will not tell iTunes to use previously added media in that new location.

So the two ways are:

1)

Apple's 6 page, exhaustively meticulous step-by-step instructions: How to move your iTunes library to a new computer - https://support.apple.com/HT204318  It is handy if you suspect any of your media are not in the standard location.

My one-sentence summary if you use iTunes' default preferences settings:  Copy the entire iTunes folder (and in doing so all its sub-folders and files) intact to the other drive, hold down the option/alt key (shift on Windows) while starting iTunes, and when requested to select a library select the iTunes Library.itl file in the copied folder (Open a different iTunes Library file or create a new one - https://support.apple.com/HT201596).

2)

iTunes 12 for Mac: Change where your iTunes files are stored - http://support.apple.com/kb/PH19507 - This should say "Change where your media files but not where your other library items are stored" - more information at: https://discussions.apple.com/message/22026652#22026652 - and steps 5-8 in https://discussions.apple.com/message/24491967#24491967. This is the consolidate process.