From Jenn E Norton at the Music Gallery.

"Projected video creates sound with photocell resister and 555 chip --> Audio signal sent out --> triggers relay --> turns blow dryer on --> tips mercury switch --> motor w/light turns --> light sensor --> relay --> turns hot plate on --> butter melts ---> micro switch --> turns on fan to play a theremin with a banana + hot plate ---> turns on second hot plate --> melts chocolate --> micro switch to relay --> turns on popcorn maker...."

555 timer chip? Woah ... flashback ...

https://www.google.com/search?q=555+timer+circuits&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjbgY75mNrRAhUGLyYKHfZFCakQ_AUICCgB&biw=1200&bih=663