In music, a diminished third is the interval produced by flattening a minor third by a chromatic semitone. In equal temperament it is enharmonic with the major second, both having a value of 100 cents. However in meantone tunings with fifths flatter than the 700 cents of equal temperament, the diminished third is wider than the major second. In 19 equal temperament it is in fact enharmonically equivalent to an augmented second, both having a value of 262.6 cents. In 31 equal temperament it has a more typical value of 232.3 cents. In a twelve-note keyboard tuned in a meantone tuning from E♭ to G♯, the dimininished third appears between C♯ and E♭, and again between G♯ and B♭. A minor third is the smaller of two commonly occurring musical intervals that span three diatonic scale degrees. ... In music, a chromatic semitone is the amount by which any note is raised by the addition of a sharp, or lowered by the addition of a flat. ... An equal temperament is a musical temperament, or system of tuning, in which an interval, usually the octave, is divided into a series of equal steps (equal frequency ratios). ... In music, an enharmonic is a note which is the equivalent of some other note, but spelled differently. ... A major second is one of three commonly occuring musical intervals that span two diatonic scale degrees; the others being the minor second, which is one semitone smaller, and the augmented second, which is one semitone larger. ... The cent is a logarithmic unit of measure used for musical intervals. ... Meantone temperament is a system of musical tuning. ... In music, 19 equal temperament, called 19-tet, 19-edo, or 19-et, is the scale derived by dividing the octave into 19 equally large steps. ... The musical interval of a minor third is the relationship between the first note (the root or tonic) and the third note in a minor scale. ... In music, 31 equal temperament, called 31-tet, 31-edo, or 31-et, is the scale derived by dividing the octave into 31 equally large steps. ...

In septimal meantone temperament the diminished third is considered to approximate the interval of a septimal major second, with ratio 8/7, and in any meantone tuning in the vicinity of 1/4 comma meantone, such as 31-equal temperament, it will come close to that value; for instance in 31-equal temperament the diminished third is a cent sharp of 8/7. In music, septimal meantone temperament, also called standard septimal meantone or simply septimal meantone, refers to the tempering of 7-limit musical intervals by a meantone temperament tuning in the range from fifths flattened by the amount of fifths for 12 equal temperament to those as flat as 19 equal...

The complementary interval to the diminished third is the augmented sixth, and the numerous chords of common practice music described as augmented sixth chords thereby contain the diminished third as well. For example, a German sixth chord E♭ G B♭ C♯ E♭' exhibits a diminished third between C♯ and E♭' which complements the augmented sixth between E♭ and C♯. In traditional music theory a complement is the interval added to another, that is placed on top of another, so that their complete span is an octave. ... An augmented sixth is one of three musical intervals that span six diatonic scale degrees. ... In music the common practice period is a long period in western musical history spanning from well before the classical era (as identified in much modern history of music), dated, on the outside, as 1600-1900. ... An augmented sixth chord is a chord which has the interval of an augmented sixth between its highest and lowest notes and also a major third above the lowest note. ...

See also

• List of meantone intervals