The main organ is located behind the 1890's facade. Although these facade pipes actually played when the first organ was installed here, they were pitched at different levels, not unusual in those days.
The OPRC organ is controlled by a state of the art console. It's actually a computer attached to keyboards. When depressed, each key send a signal to the computer which in turn sends a signal to open the small "door" attached to the windchest under each pipe. When that "door" opens it allows the air within the windchest to escape up through the pipe.
The knobs on each side of the keyboards control which row of pipes, called ranks, are to be played. Each rank of pipes (usually 61 pipes) has a specific sound and pitch. The type of sound is indicated by the name, and the pitch is indicated by the number on each drawknob. The number 8 indicates that the rank of pipes will sound at the standard pitch, like a piano. The number 4 indicates the pitch will actually be an octave higher.
When a button, called a piston and located below each keyboard, is pressed a combination of drawknobs can be either pulled out or pushed in. This is called "combination action". These pistons are programmed by the organist, enabling him or her to quickly change registrations.
The organist has 256 different levels of memory available to program the combination action. The console also has an instant transposer.