First, in order to do this right, we recommend backing up your library before snipping any cables (we also don't recommend actually snipping any cables; they can be expensive to replace). If you haven't gotten into the backup habit yet, Scott's How to Back your music using iTunes 7 tutorial is a great place to start.
Now, on with the show.
We'll begin by assuming you have already set up your AEBS (AirPort Extreme Base Station) and that you have the hard drive you're planning to use. We recommend not hooking the drive up to the AEBS just yet, as moving the typical iTunes library filled with a few GB of stuff would go a lot faster via USB than even the zippier new 802.11n wireless. With that said, and with iTunes shut down, let's get started:
- Begin just as you would with our external hard drive tutorial by plugging your USB drive directly into your Mac (the AEBS is USB-only, which means some of you might have to buy a new drive just for doing stuff like this with your new base station).
- Next, move the "iTunes Music" folder, located in ~/Music/iTunes/, to wherever you want on your external hard drive. If you also have an "iPod Games" folder in there, move that too. Just be sure to keep them together no matter where you decide to place them. Leave the Album Artwork folder, as well as the three individual library files right where they are.
- Wait a while. If you have a large library (ours was over 40GB), wait a long while.
- Once the transfer is finished, unmount the drive and hook it up to the AEBS. Give the two devices a little time to make nice.
- The AEBS by default is set to automatically mount any connected drives on your Mac (or PC), however, a strange quirk happened here: we received a dialog asking to connect to the drive with a password, even though we had never actually set up the drive with the new AirPort Utility. Of course, setting the drive to auto-mount when you connect to your AEBS network would be ideal if you want no-fuss use with iTunes (and any other 'wireless library' setups like this), but the choice is entirely up to you. Pressing cancel on this dialog, setting up the AirPort Utility to use a password for the drive and then setting it to save the pass in Keychain got us back on our way.
- Speaking of choices, you have another one to make: once you open iTunes again, it will still be looking at your local library. We need to tell iTunes the party has moved to the remote drive connected to your AEBS, and you have three options (that we know of) for accomplishing this. Your first option is to open iTunes and go to the Advanced > General tab and use the "Change..." button to tell it where your new "iTunes Music" library lives. Your second option is to give iTunes a kick-in-the-pants before you open it by moving your local /iTunes/ folder to somewhere other than where it currently resides, then opening iTunes. To be honest, we had to go with a unique combination of the two that you *shouldn't* have to deal with, but we're posting it here just in case: We actually had to move our entire /iTunes/ library to the external drive (including the Album Artwork folder and those three library files that previously shouldn't be moved), then completely delete the local copy of that /iTunes/ folder in order for iTunes to actually obey the new library location we set under that Advanced preferences tab. Like we said though: that third one isn't pretty, and it isn't recommended as your first choice.
- Either way, once everything is in its place and you choose the new library location, iTunes will likely pop up a progress window telling you that it's re-analyzing your library. That's fine - iTunes is just double-checking your handiwork.
- As a final check to make sure this all went as planned, click on any library file from within iTunes and press cmd + i (or View > Get Info). At the bottom of the Summary tab in that window is a "Where:" section that tells you the actual file path to that piece of media; be sure that path begins with the name of your AEBS-connected drive, and not "Macintosh HD," or whatever you happened to rename your main hard drive to.
- The fantastic "Consolidate Library" option under iTunes's Advanced menu might become your best friend if you happen to add a lot of media (or automatically download podcasts) while you're away from your wireless network. iTunes is smart in situations like this, but it doesn't tell you it's working some magic behind the scenes: when you're away from your media library, perhaps connected to another network or on the other side of the planet, any content you add to iTunes will be placed in that local ~/Music/iTunes/iTunes Music/ library that we just got done leaving in the dust. This, of course, might begin to annoy the manual organizers in the audience, but this is why we love the genius of Apple's software engineers: once you're connected to your media library again (and this works with our AEBS setup or an external hard drive via USB/FireWire), using that "Consolidate Library" option will tell iTunes to move all of your new media into your true library's location. In this case, since your library is on a drive connected wirelessly, iTunes will shuffle everything over to that drive. Easy breezy library management that takes a mere two clicks.
- You might notice some iTunes operations become at least a little sluggish, such as using Get Info on a file or beginning to play a video. This is natural and, at least from our limited experience so far, nothing to worry about. Just know that some things won't be insta-snappy like they were when your library was non-wireless and on a local hard drive, but music, including skipping tracks, seems to remain pretty quick with this setup.
- We haven't had a chance to try streaming our library over the web using the AEBS's new ability to open itself up to remote access. It should be entirely possible in theory, but there are plenty of factors that could affect performance on both ends, and streaming your library could turn out to be flaky or even unusable.
- We wouldn't recommend this as a solution for sharing as a library repository across multiple machines unless you're up for a little bit of repetitive effort from here on out. The problem is: every time Machine A adds a file into the library, Machine B won't know it unless you chose File > Add to Library... and select the entire /iTunes Music/ library for a re-scan. Of course, you could always manually add new files to each machine from here on out, but you can still run into quirks such as inconsistencies in metadata (ratings, etc.) and things like album art being overwritten or even deleted. If you really want to go down this path, however, you might be able to automate this manual library updating via Automator or AppleScript, but you're on your own there.