My concern with this solution is that while it may solve the problem initially described here — "I've added a new album of mp3s into my iTunes Library directory hierarchy, but the album is not showing up in the iTunes user interface" — the solution also has additional side-effects which artfromaz did not mention in his/her post, and which, I suspect, many users are not researching.
I am having the same issue, and I'm currently using iTunes 12.1.0.50 on OS X 10.10.2, but when I go under the "Store" menu and see the option to "Turn On iTunes Match", I have to wonder what is "iTunes Match"?, because it sounds like it is (or would be) more than simply a mechanism to update my iTunes UI whenever I add files into my iTunes Library directory hierarchy.
So I slide over a couple of menus, to the "Help" menu in iTunes, and I type in "iTunes Match", and I get some results. The first "Help Topic" result (which is after the "Menu Items" results) is entitled "Use iTunes Match to access all your music anytime, anywhere". I click on it, of course, so that I may read more about what the effects of turning on iTunes Match might be. This is what the top of the Help article describes:
iTunes Match is a service that safely stores all your music in iCloud—even songs imported from CDs or not purchased in the iTunes Store—and makes it available on up to 10 of your devices and computers. With iTunes Match, you have access to your complete iTunes music library at any time.
To use iTunes Match, you have to subscribe to it using your Apple ID, and turn it on on all the computers and devices where you want to use it. If you don’t have an Apple ID, you can create one during setup.
If you subscribe to iTunes Match, iTunes Radio is ad-free.
Once one has digested what the iTunes Match service is, then it becomes clear that the suggested "solution" to the originally-stated problem cannot be the correct solution. It might somehow have a side-effect of updating the library list in the UI, but that is not its primary function. For myself, if I were to turn on iTunes Match, then (at least based on the Help description) my 120G library of mp3s is going to suddenly want to update itself to iCloud, where I have 5G of free storage. Once the update was complete, would that then mean I would be paying 115G of iCloud storage space per month? And that doesn't even address the amount of time and bandwidth it would take to perform the initial moving of that 120G of data into iCloud.
There has to be a better solution, a more direct/intended solution... I'm going to try the following, which was already also suggested here:
- Quit iTunes.
- Delete the "${HOME}/Music/iTunes/iTunes Library.itl" file.
- Restart iTunes, which will allow the just-deleted file to be rebuilt, which will then pick up the newly-added files/albums.
If that's the solution which Apple intends to solve this issue, I'll say it seems rather clunky.