I’m creating something like incredibox, Need Help

Im trying to build an flash application like http://www.incredibox.com/v4/ It allow user to drag and drop to play music, and all the music synchronizing together, but it is possible to build with AC3, the only question I wanted to ask is the recording and saving function. How to make the record feature to record the background music which follow by user's sequence? And how to allow user to save the sequence as a .mp3 output? Do it need something like MySQL database to achieve it? Or all the feature like Incredibox can totally done within Adobe Flash?

Comment and opinion are welcome.