HOW TO Store your iTunes library on an external drive
1 Consolidate iTunes files
Open iTunes and click iTunes > Preferences. Click on the Advanced tab and make sure ‘Copy Files to iTunes Media folder when adding to library’ is checked. Click OK, then click on File > Library > Consolidate files.
2 Move your iTunes folder
In Finder, navigate to Music/iTunes in your account’s folder. Click once to select the iTunes folder then ≈- click to copy it. Navigate to your external drive and choose Edit > Paste. Don’t delete the original iTunes folder just yet.
3 Update iTunes
Open iTunes and click Preferences. In the Advanced Tab click on the Change button besides ‘iTunes Media Folder location’. Navigate to the new iTunes Media folder on your external drive, and click Open.