Instruments of Music & Optics - Mechanical Drum

Leonardo invented mechanised drums to be used in military marches and perhaps as soldiers went into battle.
The drums beat in complicated rhythms according to the movements of the axle of the wagon. When the cart is pulled along, the gears turn the two central rollers, which move the ten drumsticks (five on each side). The pegs or cams that are placed in the rollers can be arranged in different positions to change the beat and rhythm of the music. The loud noise created by multiple beats from one instrument could have the enemy believing that the approaching army was far greater in size than it actually was.