Leonardo da Vinci's organ gun used multiple barrels to fire several shots in quick succession.
The organ gun, also called a volley gun, arranged a group of small gun barrels so they could be loaded and fired in sequence or together. Leonardo's military studies included multi-barrel arrangements intended to increase the rate of fire compared with a single cannon.
Its name comes from the visual resemblance between the parallel barrels and the pipes of a musical organ. It was not a musical instrument. The design was a gun concept for battlefield use, intended to deliver a concentrated volley against troops.
This weapon is distinct from Leonardo's large crossbow and from the armored vehicle commonly called his tank. It also differs from a modern machine gun: the organ gun still required separate loading and did not use a continuous cartridge-feed system.