Music with 4109 pipes

There are not many instruments that are played simultaneously with hands and feet. The organ is one of them. It's not surprising that you have to use your whole body to make such a huge apparatus sound. Our organ in the Kulturpalast has a whopping 4109 pipes! How to make them produce music, what a register is, what hides behind the strange word "manual," and much more will be revealed in our school concert. Oh, and why is the organ actually in th...