Trouble with Synthesia, your keyboard, or adapter? Think you found a bug?
When describing problems, always mention your OS and game version (shown at the bottom of the title screen).
Probably 20 notes at a time in sections (all fast and changing rapidly)... I noticed it with some songs with less complexity tonight as well. It's a brand new install of windows too, just installed today, so nothing clogging up the pipes. To be honest it's not that big of a deal as this is my actual skill level is crap, but it's fun for me (and my 9yo son who is better than me) to play with. I'll give it a shot with a more recent laptop just to see if it improves things. If not, then perhaps it is the keyboard.