Thanks, I'll try that tomorrow. In regards to drops, it is indeed random - today I received one shard #3 and one shard #2 when I beat a boss (twice) today, so I'll just have to keep at it.
@Entei - It depends on your tastes. Look them up on youtube. Alternatively, if your Internet connection isn't fast enough, you can go to a website called vgmusic.com where they have user created MIDI versions of thousands of tracks that should give you an idea on how they sound.

Maybe you're just too good at this game. Lose a bit more health. I think if you lose a certain amount of health, but your combo is high you might still fight the 3rd boss.