***Caution Potential Strobe Effect*** What if you played the silence between notes? When you click the flag Scratch will ask to use your microphone and will sample how loud the room is. Make it really quiet for this step. Start some music. If Scratch samples the sound that is more quiet than that initial sample, it will grow a box correspondingly large. Work in progress?
Talked this one through with https://scratch.mit.edu/users/jay/
