Organ/Operating the Console
The console is the part of the organ where the performer sits. It includes the manuals, pedals, switches, and various other devices. This is the "cockpit" via which the organ is played.
Besides the manuals, there are many other visible items at the console. The most important are the stops or registers, which allow air to flow to certain pipes to make different sounds. In old organs, the stops are generally knobs that you pull out to activate; on newer models, and especially electrically-operated ones, they come in the form of on-off switches.
The number of stops varies considerably from organ to organ. A small practice organ with two manuals may have as few as 15-20 stops, while a massive four-manual cathedral organ can have well over a hundred.
Because there are so many switches on the average organ, it can be very time-consuming and inconvenient if you have to change stops while in the middle of a piece. For this reason, many instruments have pistons, or buttons on the side of a manual that can be pre-set to immediately turn on a specified combinations of pipes when pressed, thereby avoiding the hassle of having to individually change each pipe stop by hand. Sometimes these pistons are located near the pedals as well for the feet to operate, called toe pistons.
Old organs usually don't have pistons, meaning that all settings have to be changed manually. This usually means you'll need a registrant, a helper that stands around the organist pulling stops when needed so the organist himself doesn't need to take his hands off the keys and interrupt the music.
On many new organs, there is often a "tutti" or "sforzando" button that turns on all of the pipes for the loudest, fullest organ sound (possibly barring any percussion). There is also sometimes an "off" button that turns off all of the pipes.