What four pipes are in a musical organ?

Answer 1

A single organ pipe can play one note and one note only. Therefore; an organ with only four pipes would play exactly four notes. A small organ with one set of pipes will have as many pipes as it does keys. Even a small, modest church organ will have at least 200+ pipes.

I suspect that you may be asking about the different types or classifications of organ pipes. Organ pipes can broken down by several different classifications. The two most basic types are Flue and Reed. The former are simply whistles, no moving parts. The latter produce tone with brass tongues much like those found in a harmonica, the difference being that in an organ reed pipe a resonator is employed - this being the pipe of a reed pipe. The resonator both amplifies the tone produced by the tongue and gives it stability of pitch. It's particular shape also allows for a particular timbre - or "color" such as that of an Oboe, Clarinet or Rohrschalmei.

In these two basic categories there are further divisions. Within the flues there are open pipes and stopped pipes. There are also "half stopped" pipes such as the Rohrflute in which each pipe has a smaller pipe extending from the covered top - a chimney or "rohr".

Open pipes can be classified as Foundation, (the Principals or Diapasons) String, (Viola da Gamba, Salicional) Flute, (Melodia, Hohlflute) or Hybrid, (Gemshorn, Dolcan).

Stopped pipes are exclusively in the flute family although considerable variation exists between wide scaled (such as the Tibia Clausa) and narrow scaled (such as the Lieblichgedeckt) types.

Reed pipes fall into two general categories: Those with full length (sometimes double or triple length) resonators such as the Trumpet and Oboe and those with fractional length and resonators such as the Clarinet, Krummhorn and the various types of Regals (which are a sub-category in themselves). Within these two categories there are two sub-categories; Chorus reeds that are voiced to blend with the ensemble and Solo reeds that are designed to be used for playing melody lines or for dramatic effects such as the State Trumpet.

Another category is that of compound voices: Mixtures and voices with more than one rank. The latter are usually composed of a rank tune on pitch and another rank tuned off pitch to create a celeste, or a gentile beating caused by one rank being tuned slightly flat o sharp. Sometimes these voices contain both a flat and a sharp rank. Mixture stops are usually composed of several ranks of open, foundation pipes although flute pipes are often used in Color Mixtures. The two types or mixtures are Chorus Mixtures and Color Mixtures. Chorus Mixtures most often are composed of ranks sounding at octave, unison and fifths although elaborate "Compensating" or "Harmonic Mixtures" often contain ranks tuned to thirds, flat sevenths and other pitches of the natural harmonic scale. Color mixtures usually contain third sounding ranks (such as the Sesquialtra and Cornet) the exception to this being the Cymbal (or Zimbel) which contains only octave and fifth sounding ranks and is intended to add a sparkling effect to combinations. Foundation pipes are used in Chorus Mixtures and Cymbals, flute pipes in Color Mixtures although foundation pipes are sometimes used in combination with flute pipes in Color Mixtures. String Mixtures were once quite popular in the heyday of the orchestral organ (such as the Dolce Cornet) and String Mixtures are found in the string divisions of many large organs.

It should also be mentioned that there is a classification of pipes according to their pitches - the Mutations or Aliquots (Quint 2 2/3' Nasard 2 2/3' Tierce 1 3/5' for example) which sound at other than unison or octave pitch. These are typically pitched at fifth, third or octaves thereof although other pitches of the natural harmonic scale are sometimes seen as discussed under Mixtures. Mutations are further classified by their intended use just as are the mixtures; either for reinforcing the ensemble, in which case foundation pipes are used, or for color, in which case flute pipes are used.