I prefer to listen to my music on my laptop in Apple Lossless at home. On the go however AAC is fine, and a must, as I don't have enough space on my SSD.

Itunes has the feature to automatically convert AL to ACC when syncing with an ipod. Could this be replicated to work with another mac too? I would then have my master library (with AL) aliased to an external drive I hook up when at home, but when on the go it would fall back to my slave library (AAC) on my local SSD.

  • I would love to have a good solution to this. I'm sort of hoping the iCloud might let me choose how to "download" music to a computer. Then my main computer has AL but my notebook has only AAC (and possibly only 30% of my whole library.)
    – GreenKiwi
    Commented Aug 26, 2011 at 22:40
  • In fact, in my case, with just one laptop, and an itunes library with AL on an external HD. Using the iCloud matching feature (at 25 usd/year, + the bandwidth) might be an option, but not the most elegant.
    – newnomad
    Commented Aug 30, 2011 at 5:24

3 Answers 3


This probably can be achieved by just using iTunes Match, don't know if you're willing to subscribe to this. The master library with AL is getting matched, giving you access to the AAC versions from the cloud. From then on, everything you do to a file in your AL library is getting automatically synced to the iCloud AAC version.

When you're on the go just switch to the local SSD library. Start with an empty library, activate iTunes Match and all your music get's visible without being physically on the device. You could then download all the AAC versions from iTunes or just those you want to have on the device. All changes between your master and this slave library should get synced, you just have to manually download music on your SSD when you add something new to your master library.


I know of no way to re-use the AL -> AAC iPod conversion-on-sync for use in a playlist or library.

If you already have AAC dupes of your AL tracks, you could

  1. Duplicate-convert all AL tracks into AAC
  2. Set a smart playlist of only AAC tracks
  3. Run an Automator action to export the smart playlist to another folder
  4. Create a new iTunes library
  5. Set other folder above as the iTunes library for the SSD
  6. Option-start iTunes to switch between the two libraries
  7. Re-run the Automator playlist export to feed new tracks into the SSD library folder; import those new tracks into the SSD iTunes library

Not a very elegant solution, but perhaps an acceptable compromise depending on your requirements.


So I would suggest you a cleaner way, because I believe not all of your tracks are in Apple Lossless, so making a Smart Playlist that returns AAC tracks might return some of your original tracks.

My steps are as following:

a) Create a new iTunes library without any tracks

b) Import all tracks from your old library (Do not copy, there's an option under Preferences that will copy all your imported media to iTunes Media folder, uncheck it)

c) Convert all tracks to AAC (There's option for quality in Preferences, it's not hard to find, just rather weird, it's Import Settings..., you can choose whatever quality that you like)

d) After converting all tracks to AAC, those new tracks will reside in your new iTunes library's iTunes Media folder. Copy them to your laptop. And you can delete the new temporary library. Or you can simply copy the whole library folder over, if you'd like to.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .