Delete songs and other content in iTunes on Mac
In the iTunes app on your Mac, choose an option (Music or Movies, for example) from the pop-up menu at the top left, then click Library.
Click the item to select it, then press the Delete key.
Click Delete [item].
Do one of the following:
Remove the item only from your iTunes library: Click Keep File.
Delete the item from your computer: Click Move to Trash. The item is removed the next time you empty the Trash.
Deleting an item from a playlist doesn’t remove it from your iTunes library or your computer. Deleting a playlist or folder doesn’t remove the songs in it from your library or computer. Deleting a folder removes all the playlists and folders inside that folder.
If you can’t remove a song, make sure you didn’t select a song in a Smart Playlist with “Live updating” turned on.