Oh it is super simple. If you don't know, Peggle is a arcade/pinball style game where you try to collect points by hitting things with a ball. As you hit more things in a row, there is an audio clip that plays and it gets higher/more intense as you hit more things. You already have a sound play when a sticker activates so making it play a different sound or a higher key would be super simple.
That was just the first thing that came to mind. Feel free to completely disregard my mad ramblings haha.