Leonardo da Vinci designed an organ gun with multiple cannon barrels arranged in rows.
The weapon's barrels were mounted on a frame so that a large number of shots could be fired in succession or in a volley. The arrangement resembled the pipes of a musical organ, which explains the name later used for this type of weapon.
Leonardo's military drawings show the concept as a way to increase the rate of fire and reduce the delay between shots. Crew members could load one row while another was being fired, although the design still depended on black powder and manual reloading.
An organ gun was not a modern machine gun. It lacked automatic loading and continuous fire. The concept belongs to the history of volley guns, which used multiple barrels to deliver concentrated fire.