After disconnecting the drive I noticed that some newly added songs would not sync to my iPhone. I reconnected the external drive, checked the location of my music (which as I later found out is only updated after relaunching iTunes) and used the _File > Library > Consolidate _ . When I noticed that it was copying all my music to instead of from the external drive I canceled the process. And so I ended up with an iTunes library that thinks that my music is split between two disks even when all the music is still available in its original location.

I’ve quit iTunes and tried to fix iTunes library. iTunes keeps its music library in the file ~/Music/iTunes/iTunes Library and also exports it the XML file ~/Music/iTunes/iTunes Music Library.xml. iTunes directly uses ~/Music/iTunes/iTunes Library and will only reconstruct it from the XML file when this file is corrupt (if it’s simply deleted iTunes will start with an empty library).

First I’ve made a backup of ~/Music as these steps might make the problem even worse.

mv ~/Music/iTunes Music Library.xml ~/Music/iTunes Music Library.xml.backup

Corrupt the database by replacing it with some data, I suggest

echo 'stupid iTunes' > ~/Music/iTunes Library

Then replace all occurrences to the external hard drive with the original location. In my case the external hard drive lives at /Volumes/Music/Music and the original location was /Users/ckuijjer/Music

perl -pe 's@Volumes/Music@Users/ckuijjer@g' ~/Music/iTunes Music Library.xml.backup > ~/Music/iTunes Music Library.xml

Start iTunes and wait for it to import the XML file

Now lets see if all my iPhone applications are still there and that it still syncs with my iPhone. Also updating Time Machine as I had it configured to skip ~/Music. Changing that to skip ~/Music/iTunes/iTunes Music, e.g. skip the music files itself, but please, please backup iTunes library.