What is the difference between a piano and an organ?

Answer 1

The pipe organ is a musical instrument that produces sound when pressurized air (wind) is driven through a set of pipes. A pipe organ contains one or more sets of pipes, a wind system, and one or more keyboards. The admission of wind into the pipes is controlled by a keyboard. Each key activates at least one pipe so there must be at least one pipe for each and every key on the keyboard or pedalboard. An action connects the keys to the pipes and the action can be direct mechanical action, pneumatic action or electrical action. A pipe sounds when a key is depressed, and the action allows the wind to enter the pipe through a wind channel. Organs usually include one or more keyboards playable by the hands and one keyboard playable by the feet. Each keyboard controls a certain number of pipes. The smallest (portable) organs may have only a few dozen pipes and only one keyboard, while the largest organs feature thousand of pipes and several keyboards.

Pipes in the organ are arranged into sets called ranks or stops. This is one of the unique characteristics of the pipe organ. Stops allow the organist to control which ranks of pipes sound at any given time. Each division of the organ contains from one to several stops. The organist operates the stops and the keyboards from the console. Each stop usually controls one rank of pipes, although some stops consist of multiple ranks (such as mixtures). The name of the stop reflects the stop's timbre, pitch and construction. Stop names are not standardized: two identical stops from different organs may have different names and stops with the same name on different organs may produce different sounds. In addition, there are regional and historical differences that can result in differences in sound and what these may be called.

The organ has different stops in order to facilitate a range of tone colours and volumes. Additionally, some ranks are designed for mainly harmonic use, some mainly for solo (melodic) use and some can be used for both purposes. Pipes in the organ can be described in different 'families': flue pipes (principles/diapasons, flutes or strings) or reed pipes, and they can exist at different pitch levels. A stop that sounds at unison pitch is referred to as being at 8′ (eight-foot - pitch names in the organ are never given in metric units) pitch. This refers to the length of the lowest-sounding pipe in that rank (usually bottom C, which is approximately 8 feet long if it is an open flue pipe). A stop that sounds an octave higher is called 4′ pitch, and one that sounds an octave lower is called 16′ pitch. Stops of different pitch levels are designed to be played alone or in combinations. The higher-pitched stops reinforce the partials of the unison- and lower-pitched stops according to the natural harmonic series, adding variety or brilliance to the timbre. Each family of organ pipe has many different members that differ not only in pitch but also in the way the pipe is constructed. The main difference is whether the pipe is open at the non-speaking end or closed: a closed pipe sounds one octave lower compared to an open pipe of the same length. Also, pipes have different scales: they are relatively wider or narrower for the same length. They can be made of wood or different metals. They can be cylindrical, rectangular or tapering, and round, square or triangular in cross section. All of these features can influence the type of sound that the pipe can produce. One of the refinements of good organ playing is to know how to combine the stops.

The organ's continuous supply of wind allows it to sustain sound for as long as a key is depressed. This is unlike other keyboard instruments, such as the piano or the harpsichord, whose sound begins to decay immediately after the key is struck.

The piano is a musical instrument played by means of a single keyboard. The sound is produced by striking metal strings with felt hammers that are controlled by the keys. The hammers immediately rebound allowing the strings to continue vibrating. These vibrations are transmitted through a bridge to a soundboard that amplifies the sound. After the string is struck, however, it immediately begins to loose its energy and so the sound starts to die away. Most modern pianos have three strings per note. The strings are of different lengths and thicknesses to achieve the pitch of each note. The piano cannot produce a variety of different timbres as can the organ with its multiple stops. However, a piano can easily be played loudly or softly (hence its formal name 'pianoforte') by differences in key stroke (achieved by altering the players finger, hand or arm pressure) whereas this is not possible on the pipe organ.

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