You could always point iTunes to recognize your external HD as the library source. If you change it within the settings, it will take a little while to update your library. Most of the metadata will transfer over, but you might lose some artwork that you had to manually put in.
I did that when my MacBook started to fill up, and I now use the external as the source and leave my internal hard drive specifically for running programs.
I did that when my MacBook started to fill up, and I now use the external as the source and leave my internal hard drive specifically for running programs.