I want to put my iTunes library on an external hard drive but leave my favourite songs on the computer to access without the external hard drive and when using iMovie. Is there a way to do this?

Question

I have filled my hard drive, half with music, half with photos. I want to take my music off, and put it onto an external hard drive. However, I would still like to have access to favourite songs and playlists when the external hard drive isn't plugged in. I would also like to access this music to use with iMovie. Is there a way to do this?

Answer 1

You will have to engage a split library which means you will have to start answering questions on this forum because you will need to learn a lot about how iTunes works in order not that have a big mess at the end of it all.  It also won't be easy when the time comes to relocate it all to different drives.
You can go to advanced preferences and turn off organize media and copy to items to media folder when adding items to library.  Next read about how to selectively consolidate items to the external drive.
Sept. 2010, Consolidate selected content - https://discussions.apple.com/thread/2589812 and April 2014, https://discussions.apple.com/message/25414357
"...selected the new tracks directly in iTunes, Control-clicked on the selection, and saw that now you can consolidate selected items." - http://hints.macworld.com/article.php?story=20090919000326840
Remember that when you start iTunes without the external drive turned on iTunes will present you with a bunch of broken links.  If you have automatic downloads enabled with iCloud you may have to turn that off to prevent iTunes from repopulating your drive trying to deal with those "missing" tracks.
If you add tracks in bunches to iTunes and want them to go to different media folders you will need to either add them by holding down the option key while dragging if the desired media folder is not the one set in preferences, or by changing the media folder in preferences.  Changing media folder preferences only applies to new files added, not old ones.
Okay, I am going to stop typing because you might just reply to me, "Oh, okay, forget it," and I don't need the exercise.
What are the iTunes library files? - http://support.apple.com/kb/HT1660
More on iTunes library files and what they do - http://en.wikipedia.org/wiki/ITunes#Media_management
What are all those iTunes files? - http://www.macworld.com/article/139974/2009/04/itunes_files.html
Where are my iTunes files located? - http://support.apple.com/kb/ht1391