Beach ball for 20 seconds near beginning of every track

Question

Whenever I start a music track in iTunes, it plays normally for exactly ten seconds, then iTunes goes unresponsive and beachballs for exactly twenty seconds before becoming responsive again.
The music continues playing normally while iTunes is beachballing; there is not a single jump or stutter in the playback. I simply can't use the app between 0:10 and 0:30 of any track.
The same thing happens if I pause a track and then unpause it. If I pause it at 0:36 and then unpause it, it will play normally until 0:46, then freeze (while still playing back), then become responsive again at 1:06.
Any ideas?

Answer 1

That is about when iTunes updates and rewrites its library database (unfortunately, iTunes does not use a real database, so has to re-write the whole thing every time it makes a change). iTuens won't let you do anything while it is writing its database. But that should not take 20 seconds.
Try opening Activity monitor, and watching disk activity. You'll probably see it writing while iTunes is hung. The question then becomes, why is it taking so long?
Activity monitor will tell you how fast it is writing to data to disk. With an SSD it should be over 100MB/s, but my guess is you are not seeing that speed.