The outcome of this was a transfer of my whole iTunes library from an internal disk to an external. The phrase "hindsight is always 20/20" could not be more true in this case, as in the process I managed to break most of the links iTunes had to its mp3 files! The effect - most files I attempted to play back through iTunes showed a dreaded exclamation mark warning that they would not play back correctly as the actual file could not be located. Argh!
After a little investigation, I ended up purchasing TuneUp. Read on - this is not simply an endorsement...
Most people - such as myself until recently - might remember TuneUp as being an annoying popup which appeared some time back whenever you launched iTunes (unless you disabled the popup).
The program promises to clean your iTunes library, adding in missing tags and missing cover art, generally tidying things up. It also offers to dedupe your library so that multiple instances of the same track are removed.
Now, let me be clear. TuneUp is not a simple matter of one click and everything is sorted. To be honest, I had a frustrating problem with the program in that many times while it was "cleaning" or finding missing info, it would hang. The program requires an internet connection of course, but even when all other browsing and online activity was fine, this thing would hang and need to be restarted to pick up where it left off. Frustrating, especially if you are cleaning a large audio library for the first time.
What is TuneUp good at? The hanging issue aside, it does a good job at finding missing cover art for your tracks. It also does a good job at filling out missing or incorrect detail such as album, track or artist titles.
Deduping seemed to be a little hit and miss for my liking. Especially given that my library contained a lot of broken links given the recent hard drive changes, TuneUp didn't seem to have an ability to prioritise a track in the iTunes library that it could find over one which was a broken link in the library. As such, even on manual review of each duplicate found, it was difficult to choose the correct one to keep.
How did I get around this? A big thank you to the authors of this post titled "How To Remove Broken Songs From iTunes Library". Following these steps, I was able to remove duplicates from my library relatively quickly and easily, ensuring that broken links were completely taken out of the picture.
In summary, if you can handle the frequent need to relaunch the program, TuneUp does a good job of adding missing tags to your audio tracks and finding missing cover art. But this is how to freely and easily remove broken songs from your iTunes library.