Theory

Doubling

Doubling is when one note of a chord sounds in two voices at the same time. A triad has three different notes and four-part writing has four voices, so one note has to appear twice. The rules for this belong to part-writing.

Meaning: one chord note in two voices
Normal case: double the root in a triad
Avoid: doubling the leading tone
Reason: four voices, three different notes

Four voices, three notes

A triad consists of root, third and fifth. If you set it for four voices, say soprano, alto, tenor and bass, one of the three notes has to appear twice. This decision is called doubling. It affects the sound and the voice leading.

C major and G major, in four parts

In the C major chord (C, E, G) the root C is doubled, in the bass and in the tenor, an octave higher. In the G major chord (G, B, D) the G is doubled, in the bass and in the alto. The leading tone B appears only once.

The basic rule

Normally you double the root, which in C major is C. The root is the most stable note of the chord, and doubling it does not change the colour of the sound. The third is doubled only if the voice leading demands it, and never if it is the leading tone: a doubled leading tone would have to resolve upwards twice, and parallel octaves would result. The article The leading tone says more about the reasons.

In the dominant chord G major in C major, B is the leading tone, so the G is doubled there, as in the example. A complete seventh chord has one more note, and then the doubling often drops out altogether.

Doubling in everyday playing

On the guitar, doublings are a matter of course: the open C major shape has five notes but only three different letters, and C and E occur twice. A choir doubles too, when several voices sing the same note. The octave is the most common form.

Try it yourself: Set the three triads C, F and G for four voices and double the root each time. Check that the leading tone B in the G major chord occurs only once. You practise how the chords are put together in Build Chords.

Common mistakes

Doubling the leading tone: This leads to parallel octaves on resolution.
Always leaving out the fifth: This is allowed when it is hard to lead, but it is not the rule.
Confusing doubling with voice crossing: There voices swap positions, see voice crossing.

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Editor: Maik Krohm · reviewed on 3 October 2026

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Doubling

Four voices, three notes

C major and G major, in four parts

The basic rule

Doubling in everyday playing

Common mistakes

Continue on Maikstrings

Build Chords

The leading tone

Diatonic chords

Related terms