Most electric action and some mechanical action organs have what is called "combination action." This is a system that allows the player to change stops quickly and easily by pushing buttons under the manual keyboards called "pistons." The newest instruments today have solid-state combination actions that store information on computer memories. This multiplies the number of pistons available to the player by as many memories as the system has, allowing the entire instrument to be reset at the click of a switch. Most instruments have individual manual pistons, which control the stops of each division, as well as general pistons, which affect the entire instrument, including couplers. Some or all of the general pistons, as well as those controlling the pedal division, will usually be available on large buttons near the pedal keys called "toe studs."
Many instruments have a special piston and/or toe stud labeled "Sforzando" or "Tutti." This is a quick way to get full organ. The Tutti combination is often set by a technician and can't be changed by the player. The piston is usually a "reversible," which means that one pushes the Tutti button to bring it on and pushes it again to take it off. If there are both a Tutti button and a crescendo pedal on an organ, the Tutti combination is the louder of the two.
The tremolo (tremulant, tremblant) is a device that causes the wind supply to shake, causing the sound to waver. It may affect a single stop, a whole division, or the entire organ. The speed of the tremolo varies between instruments, and may be controlled by the player on some organs. The effect of the tremolo is more obvious than that of a celeste. It is traditionally used with the Vox Humana. It is often used with other reeds, too, particularly in lyric solos.