Diatonic and chromatic

Melodies can be based on a diatonic scale and maintain its tonal characteristics but contain many accidentals, up to all twelve tones of the chromatic scale, such as the opening of Henry Purcell's Thy Hand, Belinda, Dido and Aeneas (1689) (About this soundPlay , About this soundPlay  with figured bass), which features eleven of twelve pitches while chromatically descending by half steps,[1] the missing pitch being sung later.
Bartok - Music for Strings, Percussion and Celesta, mov. I, fugue subject: diatonic variant About this soundPlay .[2]

Diatonic (Greek: διατονική) and chromatic (Greek: χρωματική) are terms in music theory that are most often used to characterize scales, and are also applied to musical instruments, intervals, chords, notes, musical styles, and kinds of harmony. They are very often used as a pair, especially when applied to contrasting features of the common practice music of the period 1600–1900.[3]

These terms may mean different things in different contexts. Very often, diatonic refers to musical elements derived from the modes and transpositions of the "white note scale" C–D–E–F–G–A–B.[4] In some usages it includes all forms of heptatonic scale that are in common use in Western music (the major, and all forms of the minor).[5]

Chromatic most often refers to structures derived from the twelve-note chromatic scale, which consists of all semitones. Historically, however, it had other senses, referring in Ancient Greek music theory to a particular tuning of the tetrachord, and to a rhythmic notational convention in mensural music of the 14th through 16th centuries.

History

The History of the Arts and Sciences of the Antients, Charles Rollin (1768). The text gives a typically fanciful account of the term chromatic.

Greek genera

In ancient Greece there were three standard tunings (known by the Latin word genus, plural genera)[6] of a lyre.[7] These three tunings were called diatonic,[8] chromatic,[9] and enharmonic,[10] and the sequences of four notes that they produced were called tetrachords ("four strings").[11] A diatonic tetrachord comprised, in descending order, two whole tones and a semitone, such as A G F E (roughly). In the chromatic tetrachord the second string of the lyre was lowered from G to G, so that the two lower intervals in the tetrachord were semitones, making the pitches A G F E. In the enharmonic tetrachord the tuning had two quarter tone intervals at the bottom: A Gdouble flat Fhalf flat E (where Fhalf flat is F lowered by a quarter tone). For all three tetrachords, only the middle two strings varied in their pitch.[12]

Medieval coloration

The term cromatico (Italian) was occasionally used in the Medieval and Renaissance periods to refer to the coloration (Latin coloratio) of certain notes. The details vary widely by period and place, but generally the addition of a colour (often red) to an empty or filled head of a note, or the "colouring in" of an otherwise empty head of a note, shortens the duration of the note.[13] In works of the Ars Nova from the 14th century, this was used to indicate a temporary change in metre from triple to duple, or vice versa. This usage became less common in the 15th century as open white noteheads became the standard notational form for minims (half-notes) and longer notes called white mensural notation.[14][15] Similarly, in the 16th century, a form of notating secular music, especially madrigals in cut time was referred to as "chromatic" because of its abundance of "coloured in" black notes, that is semiminims (crotchets or quarter notes) and shorter notes, as opposed to the open white notes in common time, commonly used for the notation of sacred music.[16] These uses for the word have no relationship to the modern meaning of chromatic, but the sense survives in the current term coloratura.[17]

Renaissance chromaticism

The term chromatic began to approach its modern usage in the 16th century. For instance Orlando Lasso's Prophetiae Sibyllarum opens with a prologue proclaiming, "these chromatic songs,[18] heard in modulation, are those in which the mysteries of the Sibyls are sung, intrepidly," which here takes its modern meaning referring to the frequent change of key and use of chromatic intervals in the work. (The Prophetiae belonged to an experimental musical movement of the time, called musica reservata). This usage comes from a renewed interest in the Greek genera, especially its chromatic tetrachord, notably by the influential theorist Nicola Vicentino in his treatise on ancient and modern practice, 1555.[19]

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