A Yuletide Apocalypse

Note: I’m pretty sure some of the steps below are either redundant, or at least unnecessary (such as moving to the desktop, but I kept that since it helps keep things organized). So do comment on improvements to the process. This is just what I’ve been using.
SUMMARY/ALTERNATE PROCESS:
Just select the songs you want to move in the finder, and double click (or drag into iTunes). They’ll be copied, but not “re-added” as they once were (in previous versions).

So the background: I have 180 gigs of music (more or less), and a 120 gig harddrive on my laptop. So I bought a 250 gig external to hold my music. But then I started to realize, I wanted to be able to have music with me when I wasn’t carrying the external… and I also started ripping cd’s when away from home, so I amassed a sizable library on my laptop harddrive. Also, I’ve loaded up many playlists (some are historical, from my old radio shows, so worth keeping intact), and tried my best to rate the better part of my library (the ratings aren’t stored in the files, so keeping iTunes’ references intact is doubly important). So I was searching for a way to move files back and forth between my internal and external hd’s, without breaking the links in iTunes. Since iTunes references files by inode (I have no idea if this is correct, but bear with me), as opposed to file path… so merely switching your library default location, then moving the files and getting iTunes to look for the files automatically isn’t enough to update iTunes (though if you’re moving files within the same filesystem, you don’t even have to trick iTunes, since it follows the movements automatically). There’s an app that tries to fix errors in one’s library, including using spotlight and smart searching to find “missing” files from iTunes (meaning, you’d just move the files from one disk to the other, then delete from their original location, and the app would help iTunes reassociate the library entries with the newly moved files). But it doesn’t work (as of v2.1). (IDupe, by Wooden Brain Software: http://www.woodenbrain.com/sw/iDupe/idupe.html).

Here is the new method (see end of post for the old one). Only tested on MAC OS X 10.4.11 with iTunes 7.5

Some more background: the system I have currently, is that I keep a playlist with all my “local” music files (all files stored on my local hd), and all the steps below are enacted on that playlist. An easy way to make it: create an empty playlist called “local”. Drag your local music folder onto the playlist, then let iTunes freak out and load it up (and possibly reimport some of your music, since it’s just so awesome like that).

1. Go to Preferences: Advanced: General. Change your iTunes Music Folder location to the folder you want your music moved to
2. in this case, I’m moving files from my internal to the external to free up space. So I select the base folder for my external library, which is ExternalHD:Music:.
3. Make sure you have “Copy files” enabled, and I’d recommend also enabling “Keep Organized” for sanity’s sake.
4. Now iTunes will try to update the library, and reorganize things, but I just cancel all that and tell it to chill… (what does it actually do when it updates the library anyways? I have so many files, some of which are broken in the iTunes db surely, so having it recheck everything is just asking for a crash)
5. Just in case, convert the ID3 tags for the songs you want to move to the latest version (2.4). This makes sure that all the tags you’ve entered are really written to the song files (sometimes I’ve reimported files to find their tags empty!). And hopefully, prevents iTunes from not recognizing that the files you dragged are the same as their respective entries in the database. Might not make a difference, but it makes me feel better.
6. Now, move the files in question to the desktop (easy way: select one file from one of the albums, hit cmd-R to reveal the file in the Finder, then select whichever songs you want to move, and drag to desktop.)
7. The critical, and most magical, step: Drag them from the desktop back into the “Local” playlist. iTunes should give you this dialog box: “There are duplicates being added to the playlist. Would you like to add the duplicates, or skip them?”, Select “Add”. If you have an external, you might hear it tickling away as it copies the files:
8. 
9. Now you should have duplicate entries for the songs you’ve moved, in the “Local” playlist. And BOTH entries should refer to the NEW location of the files (wherever you specified in step 1). Check this with cmd-R. Now just delete all the duplicate entries (notice they BOTH have the OLD “Date Added” value!! Swwweeeet!) from the playlist (since they’re no longer “Local”.
10. Delete the files from the Desktop
11. Now you should have all the references preserved in iTunes (without actually creating or deleting any, or dealing with duplicates), the files should be neatly organized in their new home (as specified in step 1). SUCCESS!!

How to Migrate an iTunes Library (old version).
Make sure ID3 tags are up to date. Select songs in iTunes that are in old location that you want moved to new location (without iTunes knowing… in other words, it will only change where it looks for the song, the “added” date won’t change)

This is more flexible than “consolidate library” because it allows you to move only selected songs, rather than everything.

This is good for me because I keep the majority of my music on an external HD, but would like to keep SOME songs on my laptop disk so I can have music with me if I’m away from my home base and without my iPod.

So select the songs, then right click and “convert ID3 tags” to newest version (2.4).

Then move the folder(s) of songs from their current location to somewhere else on the same disk (the desktop, whatever).

Now, drag the folder into iTunes. It will copy the songs to your current Library location (be sure to have library copying turned on).

Now, go into itunes, and play the OLD version of one of the songs. It should automatically find the newly copied song, and play that instead.

You can now sort by “Date Added” and just remove all the iTunes entries you just added, but make sure you hit “Keep Files”.

Should be all set.