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Harmony

Alteration

Alteration is the chromatic change of a chord tone: a note is raised or lowered by a semitone without the chord losing its function. The chord stays what it was but gains a sharper direction, because the altered note now lies a semitone from its goal and presses towards it.

Principle
change a chord tone by a semitone
Purpose
additional leading tone
Spelling
follows the direction of resolution
Example
G7 with a lowered fifth: G–B–D♭–F

More leading tones

In a key the notes of a chord usually lie on degrees of the scale. Where the diatonic scale has a whole tone you can create a semitone by a change. That is the point of alteration: additional leading tones that press more strongly towards the goal. The chord keeps its functional name, in the example G7 stays a dominant, only one note is changed.

Without alteration: G7 (without root) resolves to C

4 4

The three upper voices of G7 (the bass G is missing): B rises to C, the seventh F falls to E, the fifth D falls to C. The bass would go from G to C.

With alteration: lowered fifth (D♭)

4 4

The D is lowered to D♭. Now the D♭ falls only a semitone to C, instead of a whole tone. The chord stays dominant but has additional tension.

In the glossary: Non-diatonic · Chromaticism

G7CG7(♭5)C

In the notation

Alterations can be recognised by accidentals that do not come from the key signature. The spelling follows the direction of the resolution: a note that goes on upwards is raised, one that goes downwards is lowered. Notes that sound the same can therefore be notated differently, depending on where they lead. In functional theory the alteration is indicated by additions to the function symbol, and the chord keeps its functional name.

Distinctions

A substitute chord is a chord built from the notes of the scale that stands in for a function, for example the tonic parallel for the tonic. Alteration, by contrast, changes a chord chromatically. It differs from modulation in that the key stays: only one note of the chord is coloured.

Practice: At the piano play G7 – C and then G7(♭5) – C, and hear how the D♭ makes the close sharper. Then try the D♯ (raised fifth), which rises a semitone to E. Note down which version you prefer, and notice in which direction the altered note resolves.

Continue on Maikstrings

The diminished seventh

A chord in which alteration becomes especially clear.

Chords

Seventh chords and chord symbols.

The leading tone

How a semitone pulls to the goal.

Related terms

Seventh chordNon-diatonicChromaticismDominantHarmonic ambiguityNinth chord

Editor: Maik Krohm · reviewed on 3 October 2026

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