My wife and I combined iTunes music libraries a few weeks back. We did it because iTunes Match is much more useful if we have 1 single library instead of it being spread out. If you are wanting to do this, here is how I did it:
- You both must be using the same iTunes Store account on all your devices (you can use separate iCloud accounts).
- We decided that my laptop would be the "authoritative" library.
- My wife went through her library and deleted anything she didn't want anymore.
- I then moved her remaining songs to my Mac over WiFi by connecting to my laptop's desktop through the finder.
- I imported about 10 artists at a time in order to manage duplicates and correct metadata (I'm picky about this.)
- I then turned on iTunes Match and let everything match and sync up.
- I then deleted everything out of her library.
- If you activate iTunes Match on another computer, it can also access the library.
You can now turn on iTunes Match on iOS by going to Settings.app > Music. If you are really daring, you can delete all your songs on your Mac. When you do this, a pop up menu will confirm that you want to delete the songs. Make sure the delete from iCloud option is unchecked. Once this happens, your entire library will be in the trash. Your music can still stream from any of your iOS devices, but you won't be taking up hard drive space on your Mac. Just make sure to keep paying for iTunes Match or you will lose access to your library. Once you have confirmed everything is working, empty your trash.