You have a bunch of "bells" (high Q metal rods) connected tightly to a nice big sounding board (the top plate). I'd be surprised if it's not got some interesting resonances.
An analogy - a tight string on a guitar makes a note when strummed. A loose un-tightened string does nothing. The under-tension lead screws are “tight strings”.
An analogy - a tight string on a guitar makes a note when strummed. A loose un-tightened string does nothing. The under-tension lead screws are “tight strings”.