Diatonic and chromatic

 ( Ancient Greek Music ) 

Diatonic and chromatic are terms in music theory that are used to characterize scales. The terms are also applied to musical instruments, intervals, chords, Musical note, , 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.

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. 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).

Chromatic most often refers to structures derived from the chromatic scale in 12-tone equal temperament, which consists of all . 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 to 16th centuries.

The intervals from one note to the next in this medieval gamut are all Whole tone or , recurring in a certain pattern with five tones (T) and two semitones (S) in any given octave. The semitones are separated as much as they can be, between alternating groups of three tones and two tones. Here are the intervals for a string of ascending notes (starting with F) from the gamut:

... –T–T–T–S–T–T–S–T–T–T–S–T– ...

T–S–T–T–S–T–T (five tones and two semitones)

The white keys are the modern analog of the gamut. In its most strict definition, therefore, a diatonic scale is one that may be derived from the pitches represented in successive white keys of the piano (or a transposition thereof). This would include the major scale, and the minor scale (same as the descending form of the melodic minor), but not the old ecclesiastical church modes, most of which included both versions of the "variable" note B/B.

Most, but not all writers,Goetschius, as cited below, accepts only the major as diatonic. accept the natural minor as diatonic. As for other forms of the minor:

• "Exclusive" usage

Some writers consistently classify the other variants of the minor scale – the melodic minor (ascending form) and the harmonic minor – as non-diatonic, since they are not transpositions of the white-note pitches of the piano. Among such theorists there is no agreed general term that encompasses the major and all forms of the minor scale.

• "Inclusive" usage

Some writers consistently include the melodic and harmonic minor scales as diatonic also. For this group, every scale standardly used in common practice music and much similar later music is either diatonic (the major, and all forms of the minor) or chromatic.

• "Mixed" usage

Still other writers mix these two meanings of diatonic (and conversely for chromatic), and this can lead to confusions and misconceptions. Sometimes context makes the intended meaning clear.

Some other meanings of the term diatonic scale take the extension to harmonic and melodic minor even further, to be even more inclusive. An explicit example of such an extended general use of diatonic scale and related terms: See also #Extended pitch selections, in this article. See also an exceptional usage by Persichetti, in a note to #Diatonic_pentatonic_scale, below.

In general, diatonic is most often used inclusively with respect to music that restricts itself to standard uses of traditional major and minor scales. When discussing music that uses a larger variety of scales and modes (including much jazz, rock, and some tonal 20th-century concert music), writers often adopt the exclusive use to prevent confusion.

 \new Staff \with { \remove "Time_signature_engraver" }
 \relative c' { \time 13/4
     

A chromatic scale consists of an ascending or descending sequence of pitches, always proceeding by . Such a sequence of pitches is produced, for example, by playing all the black and white keys of a piano in order. The structure of a chromatic scale is therefore uniform throughout—unlike major and minor scales, which have tones and semitones in particular arrangements (and an augmented second, in the harmonic minor).It is not usual to use chromatic scale in any other sense. A rare exception is found in Elements of Musical Composition, Crotch, William, 1830. (See the quotation from this text, below. See also extensive analysis in the excerpt from "The leading tone in direct chromaticism: from Renaissance to Baroque", Clough, John, 1957, in the same subsection below.) Outside of music altogether, chromatic scale may refer to Von Luschan's chromatic scale.

Forte lists the chromatic intervals in major and natural minor as the augmented unison, diminished octave, augmented fifth, diminished fourth, augmented third, diminished sixth, diminished third, augmented sixth, minor second, major seventh, major second, minor seventh, doubly diminished fifth, and doubly augmented fourth.

Additionally, the label chromatic or diatonic for an interval may depend on context. For instance, in C major, the interval C–E could be considered a chromatic interval because it does not appear in the prevailing diatonic key; conversely, in C minor it would be diatonic. This usage is still subject to the categorization of scales above, e.g. in the B–E example above, classification would still depend on whether the harmonic minor scale is considered diatonic.

In cases where intervals are equivalent, there is no difference in tuning (and therefore in sound) between them. For example, in 12-tone equal temperament and its multiples, the notes F and E represent the same pitch, so the diatonic interval C–F (a perfect fourth) sounds the same as its enharmonic equivalent—the chromatic interval C–E (an augmented third).

However, in the majority of other tunings (such as 19-tone and 31-tone equal temperament), there is a difference in tuning between notes that are enharmonically equivalent in 12-tone equal temperament. In systems based on a cycle of fifths, such as Pythagorean tuning and meantone temperament, these intervals are labelled diatonic or chromatic intervals. Under a generalized meantone tuning, notes such as G and A are not enharmonically equivalent but are instead different by an amount known as a diesis. Instruments limited to 12 pitches per octave can only produce a chain of 11 fifths, resulting in a "break" at the ends of the chain. This causes intervals that cross the break to be written as augmented or diminished chromatic intervals, with the most notable example being the "wolf interval" (which is actually a diminished sixth) that occurs when 12-note-per-octave keyboards are tuned to meantone temperaments whose fifths are flatter than those in 12-tone equal temperament. In a generalized meantone temperament, chromatic (E–E) are smaller than or equal to diatonic semitones (E–F) in size,Helmholtz, Hermann, trans. Alexander Ellis, On the Sensations of Tone, Dover, New York, 1954, pp. 433–435 and 546–548. The two notes of a diatonic semitone have different letter names; those of a chromatic semitone have the same letter name. With consonant intervals such as the major third, the nearby interval (a diminished fourth in the case of a major third) is generally less consonant.

If the tritone is assumed diatonic, the classification of written intervals on this definition is not significantly different from the "drawn from the same diatonic scale" definition above as long as the harmonic minor and ascending melodic minor scale variants are not included.

On this understanding, the diminished seventh chord built on the leading note is accepted as diatonic in minor keys."Because of the variability of scale 6 and 7, there are sixteen possible diatonic seventh chords in minor ... One __º7_____viiº⁷__" ( Tonal harmony, Kostka, Stefan and Payne, Dorothy, McGraw-Hill, 3rd edition 1995, pp. 64–65).

If the strictest understanding of the term diatonic scale is adhered to – whereby only transposed 'white note scales' are considered diatonic – even a major triad on the dominant scale degree in C minor (G–B–D) would be chromatic or altered in C minor. Some writers use the phrase "diatonic to" as a synonym for "belonging to". Therefore a chord is not said to be "diatonic" in isolation, but can be said to be "diatonic to" a particular key if its notes belong to the underlying diatonic scale of the key.

• Often musicians call diatonic harmony any kind of harmony inside the major–minor system of common practice. When diatonic harmony is understood in this sense, the supposed term chromatic harmony means little, because chromatic chords are also used in that same system.
• At other times, especially in textbooks and syllabuses for musical composition or music theory, diatonic harmony means harmony that uses only "diatonic chords". According to this usage, chromatic harmony is then harmony that extends the available resources to include chromatic chords: the augmented sixth chords, the Neapolitan sixth, chromatic seventh chords, etc.
• Since the word harmony can be used of single classes of chords ( dominant harmony, E minor harmony, for example), diatonic harmony and chromatic harmony can be used in this distinct way also.

• Chromatic harmony may be defined as the use of successive chords that are from two different keys and therefore contain tones represented by the same note symbols but with different accidentals. Four basic techniques produce chromatic harmony under this definition: modal interchange, secondary dominants, melodic tension, and chromatic mediants.

Instrumental compositions of the late Renaissance and early Baroque music periods also began experimenting with the expressive possibilities of contrasting diatonic passages of music with chromatic ones. Here, for example is part of the Virginals Piece ‘His Humour’ by Giles Farnaby. (The title ‘Humour’ should be interpreted as meaning ‘mood’, here.) The first four bars are largely diatonic. These are followed by a passage exploiting chromatic harmony, with the upper part forming an ascending, followed by a descending chromatic scale:

In the following passage from the slow movement of Beethoven's Piano Concerto No. 4, Op. 58., the long, flowing melody of the first five bars is almost entirely diatonic, consisting of notes within the scale of E minor, the movement's home key. The only exception is the G sharp in the left hand in the third bar. By contrast, the remaining bars are highly chromatic, using all the notes available to convey a sense of growing intensity as the music builds towards its expressive climax.

A further example may be found in this extract from act 3 of Richard Wagner's opera Die Walküre. The first four bars harmonize a descending chromatic scale with a rich, intoxicating chord progression. In contrast, the bars that follow are entirely diatonic, using notes only within the scale of E major. The passage is intended to convey the god Wotan putting his daughter Brünnhilde into a deep sleep.

• Alteration of a note that makes it (or the harmony that includes it) chromatic rather than diatonic."... most chromatic harmony can be read as diatonic harmony with chromatic inflection", a view attributed to Simon Sechter in New Grove, "Analysis", §II: History 3.
• Melodic movement between a diatonic note and a chromatically altered variant (from C to C in G major, or vice versa, for example)."A chromatic progression is one between harmonies with no diatonic relationship, harmonies that do not coexist in any single diatonic system of key and mode. For this purpose, the harmonic form of the minor scale is considered the tonal-harmonic basis of its diatonic system. A usual characteristic of the chromatic progression is chromatic inflection – the change of one or more notes from one form (sharp, natural, or flat) to another" Wallace Berry, Form in Music (Prentice-Hall, 1966), pp. 109–110, note 5.

• Movement between harmonies that are not elements of any common diatonic system (that is, not of the same diatonic scale: movement from D–F–A to D–F–A, for example).Wallace Berry, Form in Music (Prentice-Hall, 1966), pp. 109–110, note 5.
• The same as the second sense of chromatic inflection, above."In an the change from major to minor is supported by the chromatic progression ... in the bass" Structural Functions of Harmony, Schoenberg, Arnold, Faber & Faber, 1983, p. 54.
• In musica ficta and similar contexts, a melodic fragment that includes a chromatic semitone, and therefore includes a chromatic inflection in the second sense, above.See New Grove Online, "Musica Ficta", I, ii, cited earlier.

The term diatonic progression is used in two senses:

• Movement between harmonies that both belong to at least one shared diatonic system (from F–A–C to G–B–E, for example, since both occur in C major).See Form in Music, Berry, Wallace, Prentice-Hall, 1966, pp. 109–110, note 5. The author even includes movement between tonic and Neapolitan sixth harmonies (in both major and minor), because there exists some diatonic system in which both harmonies occur. With C major, for example, both occur in the subdominant minor, F minor.
• In musica ficta and similar contexts, a melodic fragment that does not include a chromatic semitone, even if two semitones occur contiguously, as in F–G–A.

• Diatonic modulation is modulation via a diatonic progression.Berry, Form in Music, p. 125, note 2.
• Chromatic modulation is modulation via a chromatic progression, in the first sense given above.

• One very common kind of pentatonic scale that draws its notes from the diatonic scale (in the exclusive sense, above) is sometimes called the diatonic pentatonic scale: C–D–E–G–A–C, or some other Musical mode arrangement of those notes.
• Other pentatonic scales (such as the pelog scales) may also be construed as reduced forms of a diatonic scale but are not labelled diatonic. Twentieth-Century Harmony, Persichetti, Vincent, Norton, 1961, pp. 50–51. Persichetti also makes an exceptional use of the term diatonic scale in this context: "Diatonic scales of five tones are harmonically limited ...".