Learn how the keys of the organ work. Starting with the lowest white key on the left of the piano; as you ascend to the right, the pitch will ascend. The black keys between the white keys allow you to play half steps and sound pitches halfway between the pitch of the white keys. Two white keys next to each other are also a half step away from each other.
Play a pitch on the organ by pressing any key on the organ keyboard. By playing different keys, different pipes are activated creating several different pitches for you to play.
Lower the pitch of the pipe by choosing any key on the keyboard that is lower, or to the left, of the original pitch. This will change the pitch played and lower the pitch of the pipes.