Guitar Hero Flash Replica

Hey people.

I’ve recently been playing about with designing a flash version of Guitar Hero…

If you have no idea what this is, here is a flash replica playable on the internet:

http://www.molsoncanadian.ca/coldshots/ampedup.php?

Anyway, I need a bit of advice with creating a proper engine.

A simple hit test whenever the “note” object hits the “arrow key” object is not accurate enough.

Also, the “long notes” which require holding down SPACE + Correct Key for the duration of the note.

To understand what I mean, you really have to have seen/played the game.

Thanks.