Tho still in an early stage, you can see a proof of concept overhere:
I used a midi file from piano-midi.de and exported it into a mp3 file. Then i parsed the same midifile to an XML file with a small Java program that i wrote. Flash reads in this XML file and plots the notes to stage. The position of the plotted notes is conducted by the position of the mp3 version of the song.
It is still a proof of concept: the performance has to be improved and the animation could be somewhat more spectacular.
Java and Actionscript code will be available soon.
Update 010111: i have added note info popups and a color scheme per track.