This is the last song in the campaign, and it'll be the toughest you encounter so far. Not only do you have to contend with a challenge anyway, but the game begins to fuzz your screen towards the end of the song, making it even tougher.
Luckily, you can do this on any difficulty, and you don't even have to perform any special action to reach it like the bonus songs. Just do all you can to survive the onslaught of notes and screen tampering, and once you clear the song this will pop. Nothing else fancy is required, but be warned about the dizzy fuzz it throws at you, even on normal this made me miss notes.