iPod Library Song Exchange

Drag all the soundtracks form iTunes to a folder on your external drive. Then, remove them from iTunes and let iTunes delete the files. The songs you copied across to the external are not the files that will be deleted. Now, open iTunes whilst holding OPTION and select to create a new library. Create it on the external and use the songs you've dragged over.

As a side note: there's a bug when copying a song from an iTunes library to a folder. If two songs in the group have identical song names, then none of the batch will copy, but no warning will be given. My advice to you is to make a playlist of all the songs you want and sort by song name. Then, copy them in batches and check that the file count in the folder you're copying to corresponds to the number of songs you've copied. For any double ups in terms of song names, copy the alternatives to a different location and then manually copy them back or manually reimport them to the new library later. Good luck. Hopefully that's easier than I made it sound.