Or unified system. System used in most theatre organs and in some smaller instruments (such as certain mortuary organs made by Seeburg and Operators) whereby the keyboard may be connected to the rank of pipes in several different ways. If the 8′ flute stop is selected, for example, the keyboard is connected to the rank of flute pipes so they play at normal pitch. If the 4′ flute stop is selected, the pipes play an octave higher. If the 16′ flute stop is selected, they play an octave lower. Or, by selecting the 16′, 8′ and 4′ flute stops at the same time, three pipes in the same rank play when each key is played. In contrast, a straight (or non-unified) organ has a separate rank of pipes for each stop. Because each rank of pipes in a unified organ is available at several pitches on several different manuals, a unified organ has fewer ranks of pipes in proportion to the number of stops.

Theatre pipe organ or other organ employing unification (also listed in this Glossary).

Type of pneumatic stack construction with individually-removable valve units. Each valve and pouch (and sometimes pneumatic) is contained within one unit, making servicing of defective notes easier when factory replacement units were available. Today, restoring a unit valve pneumatic stack frequently takes longer than restoring a stack made in one big chest, as there are many parts to break open for restoration instead of one big unit that usually comes apart with screws.

Small electronic organ used in some Decap and Mortier/van den Bosch dance organs built in the 1950s.

Large piano in which the strings and soundboard are mounted vertically. In descending order of size, vertical pianos are called uprights, studio uprights, consoles, and spinets.