well, you got me curious... so I looked into it. there is an open source project called StepMania that has hundreds (thousands?) of songs with the song data in various skill levels.
so, I loaded a song and the dance data, figured out how to parse it, calculated the speed the arrows have to move, and tried to get the tolerance right for hitting the targets.
this is only about half done - it doesn't keep score, count the hit statistics, combos, etc... and it doesn't calculate the note values properly - it assumes they are all quarter notes. You are supposed to read up to the next comma in the array data and then figure out the note values but that was too much for one night. Because of that, this sample will ONLY work properly with Beginner or Easy skill level.
the songs also have data for two player mode, and lots of other game features...
this will get you started, but there is a LOT more involved! it was fun figuring out this much - Good Luck!
oh, I have it using the arrow keys on the keyboard, but you will probably want to change that. Also, if you press a wrong arrow key it will kill the next note for that target - even if it should be ignored for being too far away... and lots of other issues too...