Well, I believe the game has become more personal experience instead of collective experience. What I mean by that is that it's good to keep a little level of difficulty, but at the same time it would be better to have more songs from already popular series instead of just songs from random series (example Digger T. Rock: Legend of the Lost City). Maybe add three or four songs from the round maker's personal library of games, but more than that is probably overkill.
For Nintendo kind of rounds it's OK I suppose, I mean they don't have that many franchise, and some of the most obscure ones they have I doubt they have great music in them so you can easily take them off the list.
Personally, I believe everyone should at least get 50-60% of the answers in every round, otherwise it might discourage players that wanted to try the game out and keep getting 1s and 2s every round. Well that's what I think at least.
But I know, in the end it's just for fun. With all that said, I still enjoy the Music Riddle Game here though, heck that's why I came back here at VGC actually, but making it more accessible for everyone wouldn't hurt. 
tl;dr (too long; didn't read), Mixed round sounds too vague. Should rename it Bonus or Son1x round or something! 
Random game thought :
Why is Bionic Commando Rearmed 2 getting so much hate? We finally get a real game and they're not even satisfied... I'm starting to hate the gaming community so f****** much...
