Meantone temperament

(blue), equal-tempered (black), quarter-comma meantone (red) and third-comma meantone (green). For each, the common origin is arbitrarily chosen as C. The values indicated by the scale at the left are deviations in cents with respect to equal temperament. Quarter-comma meantone, which tempers each of the twelve perfect fifths by of a syntonic comma, is the best known type of meantone temperament, and the term meantone temperament is often used to refer to it specifically. Four ascending fifths (as ) tempered by (and then lowered by two octaves) produce a just major third () (with ratio ), which is one syntonic comma (or about 22 cents) narrower than the Pythagorean third that would result from four perfect fifths. It was commonly used from the early 16th century till the early 18th, after which twelve-tone equal temperament eventually came into general use. For church organs and some other keyboard purposes, it continued to be used well into the 19th century, and is sometimes revived in early music performances today. Quarter-comma meantone can be well approximated by a division of the octave into 31 equal steps. It proceeds in the same way as Pythagorean tuning; i.e., it takes the fundamental (say, ) and goes up by six successive fifths (always adjusting by dividing by powers of to remain within the octave above the fundamental), and similarly down, by six successive fifths (adjusting back to the octave by multiplying by However, instead of using the ratio, which gives perfect fifths, this must be divided by the fourth root of , which is the syntonic comma: the ratio of the Pythagorean third to the just major third . Equivalently, one can use instead of , which produces the same slightly reduced fifths. This results in the interval being a just major third , and the intermediate seconds (, ) dividing uniformly, so and are equal ratios, whose square is . The same is true of the major second sequences and . However, there is a residual gap in quarter-comma meantone tuning between the last of the upper sequence of six fifths and the last of the lower sequence; e.g. between and if the starting point is chosen as , which, adjusted for the octave, are in the ratio of or This is in the sense opposite to the Pythagorean comma (i.e. the upper end is flatter than the lower one) and nearly twice as large. In third-comma meantone, the fifths are tempered by of a syntonic comma. It follows that three descending fifths (such as ) produce a just minor third () of ratio , which is one syntonic comma wider than the minor third resulting from Pythagorean tuning of three perfect fifths. Third-comma meantone can be very well approximated by a division of the octave into 19 equal steps. ==The tone as a mean==

The name "meantone temperament" derives from the fact that in all such temperaments the size of the whole tone, within the diatonic scale, is somewhere between the major and minor tones (9:8 and 10:9 respectively) of just intonation, which differ from each other by a syntonic comma. In any regular system the whole tone (as ) is reached after two fifths (as ) (lowered by an octave), while the major third is reached after four fifths (lowered by two octaves). It follows that in comma meantone the whole tone is exactly half of the just major third (in cents) or, equivalently, the square root of the frequency ratio of . Thus, one sense in which the tone is a mean is that, as a frequency ratio, it is the geometric mean of the major tone and the minor tone: \ \sqrt{ \tfrac{ 10 }{\ 9\ } \cdot \tfrac{\ 9\ }{ 8 }\ } = \sqrt{ \tfrac{\ 5\ }{ 4 }\ } = 1.1180340\ , equivalent to 193.157 cents: the quarter-comma whole-tone size. However, any intermediate tone qualifies as a "mean" in the sense of being intermediate, and hence as a valid choice for some meantone system. In the case of quarter-comma meantone, where the major third is made narrower by a syntonic comma, the whole tone is made half a comma narrower than the major tone of just intonation (9:8), or half a comma wider than the minor tone (10:9). This is the sense in which quarter-tone temperament is often considered "the" exemplary meantone temperament since, in it, the whole tone lies midway (in cents) between its possible extremes. ==History of meantone temperament and its practical implementation==

Mention of tuning systems that could possibly refer to meantone were published as early as 1496 (Gaffurius). Pietro Aron (Venice, 1523) was unmistakably discussing quarter-comma meantone. Lodovico Fogliani mentioned the quarter-comma system, but offered no discussion of it. The first mathematically precise meantone tuning descriptions are to be found in late 16th century treatises by Zarlino and de Salinas. Both these authors described the and meantone systems. Marin Mersenne described various tuning systems in his seminal work on music theory, Harmonie universelle, including the 31 tone equitempered one, but rejected it on practical grounds. Meantone temperaments were sometimes referred to under other names or descriptions. For example, in 1691 Huygens advocated the use of the 31 tone equitempered system as an excellent approximation for the meantone system, mentioning prior writings of Zarlino and Salinas, and dissenting from the negative opinion of . He made a detailed comparison of the frequency ratios in the system and the quarter-comma meantone temperament, which he referred to variously as temperament ordinaire, or "the one that everyone uses". (See references cited in the article Temperament Ordinaire.) Of course, the quarter-comma meantone system (or any other meantone system) could not have been implemented with high accuracy until much later, since devices that could accurately measure all pitch frequencies didn't exist until the mid-19th century. But tuners could apply the same methods that "by ear" tuners have always used: Go up by fifths, and down by octaves, or down by fifths, and up by octaves, tempering the fifths so they are slightly smaller than the just ratio. How tuners could identify a "quarter comma" reliably by ear is a bit more subtle. Since this amounts to about 0.3% of the frequency which, near middle (~264 Hz), is about one hertz, they could do it by using perfect fifths as a reference and adjusting the tempered note to produce beats at this rate. However, the frequency of the beats would have to be slightly adjusted, proportionately to the frequency of the note. Alternatively the diatonic scale major thirds can be adjusted to just major thirds, of ratio , by eliminating the beats. For 12 tone equally-tempered tuning, the fifths have to be tempered by considerably less than a (very close to a , or a ), since they must form a perfect cycle, with no gap at the end ("circle of fifths"). For meantone tuning, if one artificially stops after filling the octave with only 12 pitches, one has a residual gap between sharps and their enharmonic flats that is slightly smaller than the Pythagorean one, in the opposite direction. Both quarter-comma meantone and the Pythagorean system do not have a circle but rather a spiral of fifths, which continues indefinitely. Slightly tempered versions of the two systems that do close into a much larger circle of fifths are 31 equal temperament| for meantone, and 53 equal temperament| for Pythagorean. Although meantone is best known as a tuning system associated with earlier music of the Renaissance and Baroque, there is evidence of its continuous use as a keyboard temperament well into the 19th century. : "The mode of tuning which prevailed before the introduction of equal temperament, is called the Meantone System. It has hardly yet died out in England, for it may still be heard on a few organs in country churches. According to Don B. Yñiguez, organist of Seville Cathedral, the meantone system is generally maintained on Spanish organs, even at the present day." — It has had a considerable revival for early music performance in the late 20th century and in newly composed works specifically demanding meantone by some composers, such as Adams, Ligeti, and Leedy. ==Meantone temperaments==

A meantone temperament is a regular temperament, distinguished by the fact that the correction factor to the Pythagorean perfect fifths, given usually as a specific fraction of the syntonic comma, is chosen to make the whole tone intervals equal, as closely as possible, to the geometric mean of the major tone and the minor tone. Historically, commonly used meantone temperaments, discussed below, occupy a narrow portion of this tuning continuum, with fifths ranging from approximately 695 to 699 cents. Meantone temperaments can be specified in various ways: By what fraction of a syntonic comma the fifth is being flattened (as above), the width of the tempered perfect fifth in cents, or the ratio of the whole tone (in cents) to the diatonic semitone. This last ratio was termed by American composer, pianist and theoretician Easley Blackwood. If happens to be a rational number \ R = \scriptstyle{ \frac{\ N\ }{ D } }\ , then \ 2^{\frac{\ 3 R + 1\ }{ 5 R + 2} }\ is the closest approximation to the corresponding meantone tempered fifth within the equitempered division of the octave into \ 5\ N + 2\ D\ equal parts. Such divisions of the octave into a number of small parts greater than 12 are sometimes refererred to as microtonality, and the smallest intervals called microtones. In these terms, some historically notable meantone tunings are listed below, and compared with the closest equitempered microtonal tuning. The first column gives the fraction of the syntonic comma by which the perfect fifths are tempered in the meantone system. The second lists 5 limit rational intervals that occur within this tuning. The third gives the fraction of an octave, within the corresponding equitempered microinterval system, that best approximates the meantone fifth. The fourth gives the difference between the two, in cents. The fifth is the corresponding value of the fraction \ R = \scriptstyle{ \frac{\ N\ }{ D } }\ , and the fifth is the number \ 5\ N + 2\ D\ of equitempered ( ) microtones in an octave. Equal temperaments In neither the twelve tone equitemperament nor the quarter-comma meantone is the fifth a rational fraction of the octave, but several tunings exist which approximate the fifth by such an interval; these are a subset of the equal temperaments in which the octave is divided into some number () of equally wide intervals. Equal temperaments that are useful as approximations to meantone tunings include (in order of increasing generator width) 12 equal temperament| and . almost perfectly fits both Pythagorean tuning and 5 limit just intonation, with a few 7 limit and 11 limit intervals. The farther the tuning gets away from quarter-comma meantone, however, the less related the tuning is to harmonic ratios. This can be overcome by tempering the partials to match the tuning, which is possible, however, only on electronic synthesizers. The following table gives various meantone temperaments ==Wolf intervals==

A whole number of just perfect fifths will never add up to a whole number of octaves, because is an irrational number. If a whole number of perfect fifths is stacked-up, then in order to close that stack to fit an octave, at least one of the intervals that is enharmonically equivalent to a fifth must have a different width than all the other fifths. For example, to make a 12 note chromatic scale in Pythagorean tuning close at the octave, one of the fifth intervals must be lowered ("out-of-tune") by the Pythagorean comma; this altered fifth is called a "wolf fifth" because it sounds similar to a fifth in its interval size and seems like an out-of-tune fifth, but is actually a diminished sixth (e.g. between and ). Likewise, 11 of the 12 perfect fourths are also in tune, but the remaining fourth is actually an augmented third (rather than a true fourth). Wolf intervals are not inherent to a complete tuning system, rather they are an artifact of inadequate keyboards that do not have enough keys for all of the in-tune notes used in any given piece. Keyboard players then create a "wolf" by substituting a key that is actually in-tune with a different pitch, nearby the actual notated pitch, but not quite near enough to pass. 's isomorphic keyboard, invented in 1896. The issue can be most easily shown by using an isomorphic keyboard, with many more than just 12 keys per octave, such as that shown in Figure 2 (on an isomorphic keyboard, any given musical interval has the same shape wherever it appears, except at the edges). Here's an example: On the keyboard shown in Figure 2, from any given note, the note that's a perfect fifth higher is always upward-and-rightward adjacent to the given note. There are no wolf intervals within the note-span of this keyboard. The problem is at the edge, on the note . The note that's a perfect fifth higher than is , which is not included on the keyboard shown (although it could be included in a larger keyboard, placed just to the right of , hence maintaining the keyboard's consistent note-pattern). Because there is no button, when playing an power chord (open fifth chord), one must choose some other note, such as , to play instead of the missing . Even edge conditions produce wolf intervals only if the isomorphic keyboard has fewer buttons per octave than the tuning has enharmonically-distinct notes. For example, the isomorphic keyboard in Figure 2 has 19 buttons per octave, so the above-cited edge-condition, from to , is not a wolf interval in 12 tone equal temperament (), 17 , or 19 ; however, it is a wolf interval in 26 , 31 , and 50 ET. In these latter tunings, using electronic transposition could keep the current key's notes on the isomorphic keyboard's white buttons, such that these wolf intervals would very rarely be encountered in tonal music, despite modulation to exotic keys. Isomorphic keyboards expose the invariant properties of the meantone tunings of the syntonic temperament isomorphically (that is, for example, by exposing a given interval with a single consistent inter-button shape in every octave, key, and tuning) because both the isomorphic keyboard and temperament are two-dimensional (i.e., rank 2) entities. One-dimensional keyboards (where is some number) can expose accurately the invariant properties of only a single one-dimensional tuning in hence, the one-dimensional piano-style keyboard, with 12 keys per octave, can expose the invariant properties of only one tuning: 12 . When the perfect fifth is exactly 700 cents wide (that is, tempered by almost exactly of a syntonic comma, or exactly of a Pythagorean comma) then the tuning is identical to the familiar 12 tone equal temperament. This appears in the table above when Because of the compromises (and wolf intervals) forced on meantone tunings by the limitation of having only 12 key per octave on a conventional piano-style keyboard, well temperaments and eventually equal temperament became more popular. Using standard interval names, twelve fifths equal six octaves plus one augmented seventh; seven octaves are equal to eleven fifths plus one diminished sixth. Given this, three "minor thirds" are actually augmented seconds (for example, to ), and four "major thirds" are actually diminished fourths (for example, to ). Several triads (like and ) contain both these intervals and have normal fifths. ==Extended meantones==

All meantone tunings fall into the valid tuning range of the syntonic temperament, so all meantone tunings are syntonic tunings. All syntonic tunings, including the meantones and the various just intonations, conceivably have an infinite number of notes in each octave, that is, seven natural notes, seven sharp notes ( to ), seven flat notes ( to ) (which is the limit of the orchestral harp, which allows 21 distinct pitches per octave); then double sharp notes ( to ), double flat notes ( to ), triple sharps and flats, and so on. In fact, double sharps and flats are uncommon, but still needed, but triple sharps and flats are almost never seen, so might be skipped or compromised. In any syntonic tuning that happens to divide the octave into a small number of equally wide smallest intervals (such as 12, 19, or this extended set of notes still exists, but is not infinite, since some notes will be equivalent. For example, in and are the same pitch; in and are identical, as are and ; and in just intonation for C major, are within 8.1 ¢, and so can be tempered to be identical, with the compromise note being only a tolerable 4 ¢ off for each. Many musical instruments are capable of very fine distinctions of pitch, such as the human voice, the trombone, unfretted strings such as the violin family and fretless guitars, and lutes with movable frets. These instruments are well-suited to the use of meantone tunings. On the other hand, the conventional piano keyboard only has twelve note-producing keys per octave, making it poorly suited to any tunings other than or well temperaments. Almost all of the historic problems with the meantone temperament are caused by the failure to map meantone's infinite number of notes per octave to a finite number of piano keys. This is, for example, the source of the "wolf fifth" discussed above. When choosing which notes to map to the piano's black keys, it is convenient to choose those notes that are common to a small number of closely related keys, but this will only work up to the edge of the octave; when crossing up or down to an adjacent octave, for some of the intervals must be a "wolf fifth" – that is, slightly flatter than the others, as described above. The existence of the "wolf fifth" is one of the reasons why, before the introduction of well temperament, instrumental music generally stayed in a number of "safe" tonalities that did not involve the "wolf fifth" (which was generally put between and ). Throughout the Renaissance and Enlightenment, theorists as varied as Nicola Vicentino, Francisco de Salinas, Fabio Colonna, Marin Mersenne, Christiaan Huygens, and Isaac Newton advocated the use of meantone tunings that were extended beyond the keyboard's twelve notes, and hence these are now called "extended" meantone tunings. Such efforts required a corresponding extension of keyboard instruments to provide means of producing more than 12 notes per octave; examples include Vincento's archicembalo, Mersenne's harpsichord, Colonna's sambuca rota, and Huygens's harpsichord. Other instruments extended the keyboard by only a few notes. Some period harpsichords and organs have split / keys, such that both E major / C minor (4 sharps) and E major / C minor (3 flats) can be played with no wolf fifths. Many of those instruments also have split / keys, and a few have all the five accidental keys split. All of these alternative instruments were "complicated" and "cumbersome" (), due to : (a) not being isomorphic, and : (b) not having a transposing mechanism, which can significantly reduce the number of note-controlling buttons needed on an isomorphic keyboard (). Both of these criticisms could be addressed by electronic isomorphic keyboard instruments (such as the open-source hardware jammer keyboard), which could be simpler, less cumbersome, and more expressive than existing keyboard instruments. ==See also==