To add to SHMUPGurus's post, one idea, to start a whole new set of rounds. I think it would almost be better to separate the contests into 10 round segments. Just seems "cleaner", I mean, are you guys going to keep going forever? That's just an opinion though.
Another opinion, I think it would be better to use mostly just popular series of games. And there's nothing wrong with using multiple songs from a franchise over a few rounds; as in use a FF6 song in one round, and maybe a FF8 song the next.
Also, if you stick to more popular series, you can pick more obscure songs within the popular games (even though it's already sort of done, it's more reasonable). Also, you'll get more half points, but I think people would be happier and have more fun. It's kind of frustrating to hear some of these weird songs and REALLY think you've heard it before, but you can't place it at all. This way someone might think "Oh this is a Mario song! But which game is it from?".
Obviously, it's not perfect and there problems with that too, but I think people would be happier with scores being generally higher.
Edit: Granted, I wasn't around for the earlier rounds, so maybe it used to be something like this? I didn't go back to check.