The cent is a logarithmic unit of measure used for musical intervals. Twelve-tone equal temperament divides the octave into 12 semitones of 100 cents each. Cents are used to express small intervals, or to compare the sizes of comparable intervals in different tuning systems, in fact the interval of one cent is too small to be heard between successive notes. Alexander J. Ellis based the measure on the acoustic logarithms decimal semitone system developed by Gaspard de Prony in the 1830s, at Robert Holford Macdowell Bosanquet's suggestion. Ellis made extensive measurements of musical instruments from around the world, using cents extensively to report and compare the scales employed, further described and employed the system in his 1875 edition of Hermann von Helmholtz's On the Sensations of Tone, it has become the standard method of comparing musical pitches and intervals. Like a decibel's relation to intensity, a cent is a ratio between two close frequencies. For the ratio to remain constant over the frequency spectrum, the frequency range encompassed by a cent must be proportional to the two frequencies.
An tempered semitone spans 100 cents by definition. An octave—two notes that have a frequency ratio of 2:1—spans twelve semitones and therefore 1200 cents. Since a frequency raised by one cent is multiplied by this constant cent value, 1200 cents doubles a frequency, the ratio of frequencies one cent apart is equal to 21⁄1200 = 1200√2, the 1200th root of 2, 1.0005777895. If one knows the frequencies a and b of two notes, the number of cents measuring the interval from a to b may be calculated by the following formula: n = 1200 ⋅ log 2 Likewise, if one knows a note a and the number n of cents in the interval from a to b b may be calculated by: b = a × 2 n 1200 To compare different tuning systems, convert the various interval sizes into cents. For example, in just intonation the major third is represented by the frequency ratio 5:4. Applying the formula at the top shows that this is about 386 cents; the equivalent interval on the equal-tempered piano would be 400 cents. The difference, 14 cents, is about a seventh of a half step audible.
As x increases from 0 to 1⁄12, the function 2x increases linearly from 1.00000 to 1.05946. The exponential cent scale can therefore be approximated as a piecewise linear function, numerically correct at semitones; that is, n cents for n from 0 to 100 may be approximated as 1 + 0.0005946n instead of 2n⁄1200. The rounded error is zero when n is 0 or 100, is about 0.72 cents high when n is 50, where the correct value of 21⁄24 = 1.02930 is approximated by 1 + 0.0005946 × 50 = 1.02973. This error is well below anything humanly audible, making this piecewise linear approximation adequate for most practical purposes, it is difficult to establish. One author stated; the threshold of what is perceptible, technically known as the just noticeable difference varies as a function of the frequency, the amplitude and the timbre. In one study, changes in tone quality reduced student musicians' ability to recognize, as out-of-tune, pitches that deviated from their appropriate values by ±12 cents, it has been established that increased tonal context enables listeners to judge pitch more accurately.
Free, online web sites for self-testing are available. "While intervals of less than a few cents are imperceptible to the human ear in a melodic context, in harmony small changes can cause large changes in beats and roughness of chords."When listening to pitches with vibrato, there is evidence that humans perceive the mean frequency as the center of the pitch. One study of modern performances of Schubert's Ave Maria found that vibrato span ranged between ±34 cents and ±123 cents with a mean of ±71 cents and noted higher variation in Verdi's opera arias. Normal adults are able to recognize pitch differences of as small as 25 cents reliably. Adults with amusia, have trouble recognizing differences of less than 100 cents and sometimes have trouble with these or larger intervals. A centitone is a musical interval equal to two cents proposed as a unit of measurement by Widogast Iring in Die reine Stimmung in der Musik as 600 steps per octave and by Joseph Yasser in A Theory of Evolving Tonality as 100 steps per equal tempered whole tone.
Iring noticed that the Grad/Werckmeister and the schisma are nearly the same and both may be approximated by 600 steps per octave. Yasser promoted the decitone and millitone. For example: Equal tempered perfect fifth = 700 cents = 175.6 savarts = 583.3 millioctaves = 350 centitones. The following audio files play various intervals. In each case the first note played is middle C; the next note is sharper than C by the assigned value in cents. The two notes are played simultaneously. Note that the JND for pitch difference is 5–6 cents. Played separately, the notes may not show an audible difference, but when they are played together, beating may be hea
Jazz is a music genre that originated in the African-American communities of New Orleans, United States, in the late 19th and early 20th centuries, developed from roots in blues and ragtime. Jazz is seen by many as "America's classical music". Since the 1920s Jazz Age, jazz has become recognized as a major form of musical expression, it emerged in the form of independent traditional and popular musical styles, all linked by the common bonds of African-American and European-American musical parentage with a performance orientation. Jazz is characterized by swing and blue notes and response vocals and improvisation. Jazz has roots in West African cultural and musical expression, in African-American music traditions including blues and ragtime, as well as European military band music. Intellectuals around the world have hailed jazz as "one of America's original art forms"; as jazz spread around the world, it drew on national and local musical cultures, which gave rise to different styles. New Orleans jazz began in the early 1910s, combining earlier brass-band marches, French quadrilles, biguine and blues with collective polyphonic improvisation.
In the 1930s arranged dance-oriented swing big bands, Kansas City jazz, a hard-swinging, improvisational style and Gypsy jazz were the prominent styles. Bebop emerged in the 1940s, shifting jazz from danceable popular music toward a more challenging "musician's music", played at faster tempos and used more chord-based improvisation. Cool jazz developed near the end of the 1940s, introducing calmer, smoother sounds and long, linear melodic lines; the 1950s saw the emergence of free jazz, which explored playing without regular meter and formal structures, in the mid-1950s, hard bop emerged, which introduced influences from rhythm and blues and blues in the saxophone and piano playing. Modal jazz developed in the late 1950s, using the mode, or musical scale, as the basis of musical structure and improvisation. Jazz-rock fusion appeared in the late 1960s and early 1970s, combining jazz improvisation with rock music's rhythms, electric instruments, amplified stage sound. In the early 1980s, a commercial form of jazz fusion called smooth jazz became successful, garnering significant radio airplay.
Other styles and genres abound in the 2000s, such as Afro-Cuban jazz. The origin of the word "jazz" has resulted in considerable research, its history is well documented, it is believed to be related to "jasm", a slang term dating back to 1860 meaning "pep, energy". The earliest written record of the word is in a 1912 article in the Los Angeles Times in which a minor league baseball pitcher described a pitch which he called a "jazz ball" "because it wobbles and you can't do anything with it"; the use of the word in a musical context was documented as early as 1915 in the Chicago Daily Tribune. Its first documented use in a musical context in New Orleans was in a November 14, 1916 Times-Picayune article about "jas bands". In an interview with NPR, musician Eubie Blake offered his recollections of the slang connotations of the term, saying, "When Broadway picked it up, they called it'J-A-Z-Z', it wasn't called that. It was spelled'J-A-S-S'; that was dirty, if you knew what it was, you wouldn't say it in front of ladies."
The American Dialect Society named it the Word of the Twentieth Century. Jazz is difficult to define because it encompasses a wide range of music spanning a period of over 100 years, from ragtime to the rock-infused fusion. Attempts have been made to define jazz from the perspective of other musical traditions, such as European music history or African music, but critic Joachim-Ernst Berendt argues that its terms of reference and its definition should be broader, defining jazz as a "form of art music which originated in the United States through the confrontation of the Negro with European music" and arguing that it differs from European music in that jazz has a "special relationship to time defined as'swing'". Jazz involves "a spontaneity and vitality of musical production in which improvisation plays a role" and contains a "sonority and manner of phrasing which mirror the individuality of the performing jazz musician". In the opinion of Robert Christgau, "most of us would say that inventing meaning while letting loose is the essence and promise of jazz".
A broader definition that encompasses different eras of jazz has been proposed by Travis Jackson: "it is music that includes qualities such as swing, group interaction, developing an'individual voice', being open to different musical possibilities". Krin Gibbard argued that "jazz is a construct" which designates "a number of musics with enough in common to be understood as part of a coherent tradition". In contrast to commentators who have argued for excluding types of jazz, musicians are sometimes reluctant to define the music they play. Duke Ellington, one of jazz's most famous figures, said, "It's all music." Although jazz is considered difficult to define, in part because it contains many subgenres, improvisation is one of its defining elements. The centrality of improvisation is attributed to the influence of earlier forms of music such as blues, a form of folk music which arose in part from the work songs and field hollers of African-American slaves on plantations; these work songs were structured around a repetitive call-and-response pattern, but early blues was improvisational.
Classical music performance is evaluated more by its fidelity to the musical score, with less attention given to interpretation and accompaniment. The classical performer's goal is to play the composition. In contrast, jazz is characterized by the product of i
A clef is a musical symbol used to indicate the pitch of written notes. Placed on a stave, it indicates the pitch of the notes on one of the lines; this line serves as a reference point by which the names of the notes on any other line or space of the stave may be determined. There are three forms of clef used in modern music notation: F, C, G; each form assigns its reference note to a line depending on its placement on the stave. Once one of these clefs has been placed on one of the lines of the stave, the other lines and spaces are read in relation to it; the use of different clefs makes it possible to write music for all instruments and voices, regardless of differences in tessitura. Because the modern stave has only five lines, it is not possible to represent all pitches playable by the orchestra with only one clef with the use of ledger lines; the use of different clefs for various instruments and voices allows each part to be written comfortably on the stave with a minimum of ledger lines.
To this end, the G-clef is used for high parts, the C-clef for middle parts, the F-clef for low parts—with the notable exception of transposing parts, which are written at a pitch different from their sound even in a different octave. To facilitate writing for different tessituras, any of the clefs may theoretically be placed on any line of the stave; the further down on the stave a clef is positioned, the higher the tessitura. Since there are five lines on the stave, three clefs, it might seem that there would be fifteen possible clefs. Six of these, are redundant clefs; that leaves nine possible distinct clefs, all of which have been used historically: the G-clef on the two bottom lines, the F-clef on the three top lines, the C-clef on any line of the stave except the topmost, earning the name of "movable C-clef". Each of these clefs has a different name based on the tessitura. In modern music, only four clefs are used regularly: treble clef, bass clef, alto clef, tenor clef. Of these, the treble and bass clefs are by far the most common.
The tenor clef is used for the upper register of several instruments that use bass clef, while the alto is only used by the viola and a few other instruments. Here follows a complete list of the clefs, along with a list of instruments and voice parts notated with them; each clef is shown in its proper position on the stave, followed by its reference note.† Where the G-clef is placed on the second line of the stave, it is called the treble clef. This is the most common clef used today, the first clef that those studying music learn, the only G-clef still in use. For this reason, the terms G-clef and treble clef are seen as synonymous; the treble clef was used to mark a treble, or pre-pubescent, voice part. Among the instruments that use treble clef are the violin, oboe, cor anglais, all clarinets, all saxophones, trumpet, vibraphone, mandolin, recorder. Treble clef is the upper stave of the grand stave used for keyboard instruments, it is sometimes used, along with tenor clef, for the highest notes played by bass-clef instruments such as the cello, double bass and trombone.
The viola sometimes uses treble clef for high notes. Treble clef is used for the soprano, mezzo-soprano, alto and tenor voices; when sung, a tenor singer will sing the piece an octave lower, is written using an octave clef or double-treble clef. † In the seventeenth and eighteenth centuries, a special clef was used for violin music that published in France. For this reason it is known as the French clef or French violin clef, although it was more used for flute music; the G-clef is placed on the first line of the stave and is identical to the bass clef transposed up two octaves. When the F-clef is placed on the fourth line, it is called the bass clef; this is the only F-clef used today so that the terms "F-clef" and "bass clef" are regarded as synonymous. This clef is used for the cello, double bass, bass guitar, contrabassoon, baritone horn and timpani, it is used for the lowest notes of the horn, for the baritone and bass voices. Tenor voice is notated in bass clef when the bass are written on the same stave.
Bass clef is the bottom clef in the grand stave for keyboard instruments. The contrabassoon, double bass, electric bass sound an octave lower than the written pitch. † When the F-clef is placed on the third line, it is called the baritone clef. This clef was used for the left hand of keyboard music as well as the baritone part in vocal music; the baritone clef has the less common variant as a C clef placed on the 5th line, equivalent. † Where the F-clef is placed on the fifth line, it is called the sub-bass clef. It is identical to the treble clef transposed down 2 octaves; this clef was used by Johannes Ockeghem and Heinrich Schütz to write low bass parts, making a late appearance in Ba
In music, a chorus effect occurs when individual sounds with the same time, similar pitches converge and are perceived as one. While similar sounds coming from multiple sources can occur as in the case of a choir or string orchestra, it can be simulated using an electronic effects unit or signal processing device; when the effect is produced none of the constituent sounds are perceived as being out of tune. It is characteristic of sounds with a rich, shimmering quality that would be absent if the sound came from a single source; the shimmer occurs because of beating. The effect is more apparent; the chorus effect is easy to hear when listening to a choir or string ensemble. A choir has multiple people singing each part. A string ensemble has multiple violinists and multiples of other stringed instruments. Although most acoustic instruments cannot produce a chorus effect by themselves, some instruments can produce it as part of their own design; the effect can make these acoustic instruments sound fuller and louder than by using a single tone generator.
Some examples: Piano - Each hammer strikes a course of multiple strings tuned to nearly the same pitch. Professional piano tuners control the mistuning of each string to add movement without losing clarity. However, in some poorly-cared instruments, the effect is more prominent. Santur - As well as on the piano, the player can strike a course of multiple strings tuned to nearly the same pitch; as the instrument is tuned by the musicians themselves, the chorus effect is more heard than on the piano. 12-string guitar, bajo sexto and greek bouzouki - Courses with pairs of strings, tuned in octaves and unisons, create a distinctive complex shimmer. In the 12-string guitar, this effect is accentuated by the use of open and modal tunings, such as open-G and DADGAD. Colombian tiple, guitarrón chileno and tricordia - Courses of 3 strings, tuned in octaves and unisons, create a more complex shimmer and a fuller effect. Mandolin and oud - Courses with pairs of identically-tuned strings, as opposed to octaves and unisons on the 12-string guitar.
Accordion - two or three reed blocks tuned to nearly the same pitch produce a unique and distinctive sound exclusive to the accordion. Pipe organ - The voix céleste is an organ stop consisting of either one or two ranks of pipes out of tune; the term celeste refers to a rank of pipes detuned so as to produce a beating effect when combined with a tuned rank. It is used to refer to a compound stop of two or more ranks in which at the ranks are detuned relative to each other. However, while the open strings of a standard-tuned guitar can't produce any chorus effect, it can be obtained by the use of alternative tunings; the chorus effect can be simulated by signal processing equipment. The signal processor may be software running on a computer, software running in a digital effect processor, or an analog effect processor. If the processor is hardware-based, it may be packaged as a pedal, a rack-mount module, a table-top device, built into an instrument amplifier, or built into some electronic instruments, such as synthesizers, electronic pianos and Hammond organs.
Regardless of the technology or form factor, the processor achieves the effect by taking an audio signal and mixing it with one or more delayed, pitch-modulated copies of itself. The pitch of the added voices is modulated by an LFO, which makes the overall effect similar to that of a flanger, except with longer delays and without feedback. In the case of the synthesizer, the effect can be achieved by using multiple detuned oscillators for each note, or by passing all the notes played through a separate electronic chorus circuit. Stereo chorus effect processors produce the same effect, but it is varied between the left and right channels by offsetting the delay or phase of the LFO; the effect is thereby enhanced because sounds are produced from multiple locations in the stereo field. Used on instruments like "clean" electric guitar and keyboards, it can yield dreamy or ambient sounds. Commercial chorus effect devices include controls that enable them to be used to produce delay, reverberation, or other related effects that use similar hardware, rather than as chorus effects.
In spite of the name, most electronic chorus effects do not emulate the acoustic ensemble effect. Instead, they create a moving electronic shimmer. Although the electronic chorus effect can be obtained by the multiple ways mentioned above, some devices have adquired a high status among musicians in the "effect pedal" form. Boss CE-1 - Released in 1976, it was one of the first chorus effect pedals commercially available, based on the same circuit from the Roland Jazz C
In music, there are two common meanings for tuning: Tuning practice, the act of tuning an instrument or voice. Tuning systems, the various systems of pitches used to tune an instrument, their theoretical bases. Tuning is the process of adjusting the pitch of one or many tones from musical instruments to establish typical intervals between these tones. Tuning is based on a fixed reference, such as A = 440 Hz; the term "out of tune" refers to a pitch/tone, either too high or too low in relation to a given reference pitch. While an instrument might be in tune relative to its own range of notes, it may not be considered'in tune' if it does not match the chosen reference pitch; some instruments become'out of tune' with temperature, damage, or just time, must be readjusted or repaired. Different methods of sound production require different methods of adjustment: Tuning to a pitch with one's voice is called matching pitch and is the most basic skill learned in ear training. Turning pegs to decrease the tension on strings so as to control the pitch.
Instruments such as the harp and harpsichord require a wrench to turn the tuning pegs, while others such as the violin can be tuned manually. Modifying the length or width of the tube of a wind instrument, brass instrument, bell, or similar instrument to adjust the pitch; the sounds of some instruments such as cymbals are inharmonic—they have irregular overtones not conforming to the harmonic series. Tuning may be done aurally by sounding two pitches and adjusting one of them to match or relate to the other. A tuning fork or electronic tuning device may be used as a reference pitch, though in ensemble rehearsals a piano is used. Symphony orchestras and concert bands tune to an A440 or a B♭ provided by the principal oboist or clarinetist, who tune to the keyboard if part of the performance; when only strings are used the principal string has sounded the tuning pitch, but some orchestras have used an electronic tone machine for tuning. Interference beats are used to objectively measure the accuracy of tuning.
As the two pitches approach a harmonic relationship, the frequency of beating decreases. When tuning a unison or octave it is desired to reduce the beating frequency until it cannot be detected. For other intervals, this is dependent on the tuning system being used. Harmonics may be used to facilitate tuning of strings. For example touching the highest string of a cello at the middle while bowing produces the same pitch as doing the same a third of the way down its second-highest string; the resulting unison is more and judged than the quality of the perfect fifth between the fundamentals of the two strings. In music, the term open string refers to the fundamental note of the full string; the strings of a guitar are tuned to fourths, as are the strings of the bass guitar and double bass. Violin and cello strings are tuned to fifths. However, non-standard tunings exist to change the sound of the instrument or create other playing options. To tune an instrument only one reference pitch is given; this reference is used to tune one string, to which the other strings are tuned in the desired intervals.
On a guitar the lowest string is tuned to an E. From this, each successive string can be tuned by fingering the fifth fret of an tuned string and comparing it with the next higher string played open; this works with the exception of the G string, which must be stopped at the fourth fret to sound B against the open B string above. Alternatively, each string can be tuned to its own reference tone. Note that while the guitar and other modern stringed instruments with fixed frets are tuned in equal temperament, string instruments without frets, such as those of the violin family, are not; the violin and cello are tuned to beatless just perfect fifths and ensembles such as string quartets and orchestras tend to play in fifths based Pythagorean tuning or to compensate and play in equal temperament, such as when playing with other instruments such as the piano. For example, the cello, tuned down from A220, has three more strings and the just perfect fifth is about two cents off from the equal tempered perfect fifth, making its lowest string, C-, about six cents more flat than the equal tempered C.
This table lists open strings on their standard tunings. Violin scordatura was employed in the 17th and 18th centuries by Italian and German composers, Biagio Marini, Antonio Vivaldi, Heinrich Ignaz Franz Biber, Johann Pachelbel and Johann Sebastian Bach, whose Fifth Suite For Unaccompanied Cello calls for the lowering of the A string to G. In Mozart's Sinfonia Concertante in E-flat major, all the strings of the solo viola are raised one half-step, ostensibly to give the instrument a brighter tone so the solo violin does not overshadow it. Scordatura for the violin was used in the 19th and 20th centuries in works by Niccolò Paganini, Robert Schumann, Camille Saint-Saëns and Béla Bartók. In Saint-Saëns' "Danse Macabre", the high string of the violin is lower half a tone to the E♭ so as to have the most accented note of the main theme sound on an open string. In Bartók's Contrasts, the violin is tuned G♯-D-A-E♭ to facilitate the playing of tritones on open strings. American folk violinists of the Appalachians and Ozarks employ alternate tunings for dance songs and
Accordions are a family of box-shaped musical instruments of the bellows-driven free-reed aerophone type, colloquially referred to as a squeezebox. A person who plays the accordion is called an accordionist; the concertina and bandoneón are related. The instrument is played by compressing or expanding the bellows while pressing buttons or keys, causing pallets to open, which allow air to flow across strips of brass or steel, called reeds; these vibrate to produce sound inside the body. Valves on opposing reeds of each note are used to make the instrument's reeds sound louder without air leaking from each reed block; the performer plays the melody on buttons or keys on the right-hand manual, the accompaniment, consisting of bass and pre-set chord buttons, on the left-hand manual. The accordion is spread across the world. In some countries it is used in popular music, whereas in other regions it tends to be more used for dance-pop and folk music and is used in folk music in Europe, North America and South America.
In Europe and North America, some popular music acts make use of the instrument. Additionally, the accordion is used in cajun, jazz music and in both solo and orchestral performances of classical music; the piano accordion is the official city instrument of California. Many conservatories in Europe have classical accordion departments; the oldest name for this group of instruments is harmonika, from the Greek harmonikos, meaning "harmonic, musical". Today, native versions of the name accordion are more common; these names refer to the type of accordion patented by Cyrill Demian, which concerned "automatically coupled chords on the bass side". Accordions have many types. What may be technically possible to do with one accordion could be impossible with another: Some accordions are bisonoric, producing different pitches depending on the direction of bellows movement Others are unisonoric and produce the same pitch in both directions; the pitch depends on its size. Some use a chromatic buttonboard for the right-hand manual Others use a diatonic buttonboard for the right-hand manual Yet others use a piano-style musical keyboard for the right-hand manual Some can play in different registers Craftsmen and technicians may tune the same registers differently, "personalizing" the end result, such as an organ technician might voice a particular instrument The bellows is the most recognizable part of the instrument, the primary means of articulation.
Similar to a violin's bow, the production of sound in an accordion is in direct proportion to the motion of the player. The bellows is located between the right- and left-hand manuals, is made from pleated layers of cloth and cardboard, with added leather and metal, it is used to create pressure and vacuum, driving air across the internal reeds and producing sound by their vibrations, applied pressure increases the volume. The keyboard touch is not expressive and does not affect dynamics: all expression is effected through the bellows. Bellows effects include: Volume control and fade Repeated change of direction, popularized by musicians such as Renato Borghete and Luiz Gonzaga, extensively used in Forró, called resfulengo in Brazil Constant bellows motion while applying pressure at intervals Constant bellows motion to produce clear tones with no resonance Using the bellows with the silent air button gives the sound of air moving, sometimes used in contemporary compositions for this instrument The accordion's body consists of two wooden boxes joined together by the bellows.
These boxes house reed chambers for the right- and left-hand manuals. Each side has grilles in order to facilitate the transmission of air in and out of the instrument, to allow the sound to project better; the grille for the right-hand manual is larger and is shaped for decorative purposes. The right-hand manual is used for playing the melody and the left-hand manual for playing the accompaniment; the size and weight of an accordion varies depending on its type and playing range, which can be as small as to have only one or two rows of basses and a single octave on the right-hand manual, to the standard 120-bass accordion and through to large and heavy 160-bass free-bass converter models. The accordion is an aerophone; the manual mechanism of the instrument either enables the air flow, or disables it: The term accordion covers a wide range of instruments, with varying components. All instruments have reed ranks of some format. Not all have switches; the most typical accordion is the piano accordion, used for many musical genres.
Another type of accordion is the button accordion, used in several musical traditions, including Cajun and Tejano music and Austro-German Alpine music, Argentinian tango music. Different systems exist for the right-hand manual of an accordion, used for playing the melody; some use a button layout arranged in another, while others use a piano-style keyboard. Each system has different claimed benefits by those, they are used to define one accordion or another as a different "type": Chromatic button accordions and the bayan, a Russian variant, use a buttonboard where notes are arranged chromatically. Two major systems exist, referred to as the B-
Registration is the technique of choosing and combining the stops of a pipe organ in order to produce a particular sound. Registration can refer to a particular combination of stops, which may be recalled through combination action; the registration chosen for a particular piece will be determined by a number of factors, including the composer's indications, the time and place in which the piece was composed, the organ the piece is played upon, the acoustic in which the organ resides. The pitch produced by a pipe is a function of its length. An organ stop may be tuned to sound the pitch associated with the key, pressed, or it may speak at a fixed interval above or below this pitch; some stops are tuned to notes "in-between" the octaves and are called "Mutations". The pitch of a rank of pipes is denoted by a number on the stop knob. A stop that speaks at unison pitch is known as an 8′ stop; this nomenclature refers to the approximate length of the longest pipe in that rank. The octave sounded by a given pipe is inversely exponentially proportional to its length, meaning that a 4′ stop speaks one octave higher than an 8′ stop.
A 2′ stop speaks one octave higher than a 4′ stop. Conversely, a 16′ stop speaks one octave below an 8′ stop. Lengths used in actual organs include 64′, 32′, 16′, 8′, 4′, 2′, 1′, 1⁄2′. Example: Ranks that do not speak at a unison or octave pitch, but rather at a non-octave interval to the unison pitch, are called mutation stops; because they sound at intervals other than an octave above or below the unison sound, they are used on their own. Like the unison and octave stops, the length label of a mutation stop indicates what pitch the rank sounds. For example, a stop labeled 22⁄3' sounds at the interval of a twelfth above unison pitch; that is, with a 22⁄3' stop drawn, pressing middle C sounds the G, the 12th diatonic note above. Mutations sound at pitches in the harmonic series of the fundamental. In some large organs, non-harmonic mutations are used infrequently, as there is more "fundamental" to support; such mutations that sound at the fifth just above or below the fundamental, can create the impression of a stop an octave lower than the fundamental when low frequencies are involved.
Whenever possible or practical, mutations are tuned a mean tone interval away from the fundamental. Certain stops called mixtures contain multiple ranks of pipes sounding at consecutive octaves and fifths above unison pitch; the number of ranks in a mixture is denoted by a Roman numeral on the stop knob. So for every key pressed, five different pipes sound. In the seventeenth century, national styles of organ building began to emerge. Organs had certain unique characteristics that were common to organs in the country in which they were built. Registration techniques developed that mirrored the characteristics in the organs of each national style. A combination action is a system designed to store specific organ registrations to be recalled instantaneously by the player while they are playing, it consists of several numbered pistons situated in the space between the manuals at the organ console. The pistons control either the stops of a particular division; each piston is programmed by the organist with a particular registration to be activated when it is pressed.
This allows the organist to change registrations without the assistance of a registrant. Over the years, organ builders have designed various combination action systems; the simplest combination actions are toe studs that move a predetermined combination of stop knobs when pressed. Depending on the way in which the mechanism operates, these toe studs may not be reversible. More complex versions of this system are reversible, furthermore can activate a predetermined registration without moving the stop knobs. Certain large organs of the romantic era feature this kind of combination action; the toe studs will be labeled with dynamic markings reflecting the loudness of the registrations which result when they are pressed. For example, an organ may have two of these combinations, one labeled one labeled ff; this system allows the organist to set the stops to a specific registration and suddenly change it for a short period of time by pressing the appropriate toe stud. The organist can return to the original registration by pressing the toe stud again.
This is helpful when playing the organ works of German romantic composers such as Max Reger and Franz Liszt. The combination action in the organ at the church of Saint-Sulpice in Paris deserves special mention, it was designed by the renowned French organ builder Aristide Cavaillé-Coll. Because the organ predates the adv