Diatonic Function - Diatonic Functions of Notes and Chords

Diatonic Functions of Notes and Chords

Each degree of a diatonic scale, as well as each of many chromatically-altered notes, has a different diatonic function as does each chord built upon those notes. A pitch or pitch class and its enharmonic equivalents have different meanings. For example, a C♯ cannot substitute for a Db, even though in equal temperament they are identical pitches, because the D♭ can serve as the minor third of a B♭ minor chord while a C♯ cannot, and the C♯ can serve as the fifth degree of an F♯ major scale, while a D♭ cannot.

In music theory, as it is commonly taught in the US, there are seven different functions. In Germany, from the theories of Hugo Riemann, there are only three, and functions other than the tonic, subdominant and dominant are called their "parallels" (US: "relatives"). See Functional harmony. For instance, in the key of C major, an A minor (chord, scale, or, sometimes, the note A itself) is the Tonic parallel, or Tp. (German musicians use only uppercase note letters and Roman numeral abbreviations, while in the US, upper- and lowercase are usually used to designate major or augmented, and minor or diminished, respectively.) In the US, it would be referred to as the "relative minor".

As d'Indy summarizes:

1. There is only one chord, a perfect chord; it alone is consonant because it alone generates a feeling of repose and balance;
2. this chord has two different forms, major and minor, depending whether the chord is composed of a minor third over a major third, or a major third over a minor;
3. this chord is able to take on three different tonal functions, tonic, dominant, or subdominant.

In the United States, Germany, and other places the diatonic functions are:

Note that the ii, iii, vi, and vii are lowercase; this is because in relation to the key, they are minor chords. Without accidentals, the vii is a diminished vii°.

The degrees listed according to function, in hierarchical order according to importance or centeredness (related to the tonic): I, V, IV, vi, iii, ii, vii°. The first three chords are major, the next three are minor, and the last one is diminished.

The tonic, subdominant, and dominant chords, in root position, each followed by its parallel. The parallel is formed by raising the fifth a whole tone; the root position of the parallel chords is indicated by the small noteheads.