It showed the zodiac , the solar and lunar orbits , a crescent moon-shaped pointer traveling across a gateway that made some doors to open every hour , and five robotic musicians who play music when levers hit them . It displayed the zodiac , the solar and lunar orbits , a crescent moon-shaped pointer traveling across a gateway causing automatic doors to open every hour , and five robotic musicians who played music when struck by levers operated by a camshaft attached to a water wheel .