An observation

This is a rather clever device for those that often get flies in their kitchens..... or those that are students, everywhere.
It has some sort of chemical coating on it that attracts flies to the flower and then glues them to it. You hear them struggling and buzzing for days.
After about the second day of hearing this 'poor' fly buzzing, and struggling trying to free itself from the ever so sticky trap.
I decided to take a closer look, watching it flap and buzz its little wings.
I feel a little guilty but the buzzing was rather annoying I decided to glue its wings down. In the hope that the buzz would stop and as surprised to find that that so distinctive house fly buzz continued. Admittedly quieter but the wings where no longer movable.
So is the buzzing noise not the vibrations of the wings against the air but a vibration or movement from another part of the body.
Can anyone tell me WHAT MAKES A FLY BUZZ?