When a three-note chord is used in four-part harmony, one of the triad notes must be used twice.   This is called “doubling” a note.

SATB doubling

The doubled note can be the root, 3rd or 5th of the triad.

Following the doubling guidelines will help you to write good harmony, but do bear in mind that they are guidelines, not rules, so you may find exceptions in published music.

When choosing the note to double, you need to be aware of:

  • the inversion the chord is in, and
  • whether it is major, minor, diminished or augmented.
Root Position Chords
Most commonly doubled: root
Also possible: 5th
Rare but possible: 3rd in minor or diminished chords
Best avoided: 3rd in major chords
If you are writing a single, isolated chord for a harmony exercise, there is nothing more to consider.  

But if you are writing a number of chords (either in an exercise, or composition), then the right note to double will also depend on what’s coming next.

See the unit on Voice Leading for more on this.  

Important: always avoid doubling the leading note (7th degree of the scale).
First Inversion Chords
Major and minor chords: root, 3rd or 5th
Diminished/augmented chords: 3rd
Second inversion Chords
Always double: 5th


Sometimes in four-part harmony it may be necessary to miss out (“omit”) one note from the triad, to avoid other problems, such as consecutive 5ths.

  • Never omit the root.
  • Never omit the 3rd (except in added 7th chords).
  • The 5th may be omitted, but not in 2nd inversion chords or diminished chords.
  • If the 5th is omitted, the root may be doubled or tripled. The 3rd may be doubled but not tripled.


Although there are many ways you can write notes in a four-part chord, some combinations sound better than others. This does not just depend on doubling, but also on spacing [1]. Spacing is the vertical distance (harmonic interval) between each of the four notes in the chord.

For clear sounding harmony, we need to avoid writing low notes that are too close together. The lower the bass part is, the wider the space needed between tenor and bass.

A good rule of thumb is to keep a minimum of a 5th between tenor and bass (unless the bass note is particularly high on the stave).

Between the soprano and alto, and between alto and tenor, it is usually best to keep the parts quite close together, with a maximum of an octave between any two parts. Ideally, the parts should be less than an octave apart most of the time.

Here are some examples. Look at each chord, decide for yourself whether the spacing is good or not, then check below.

SATB spacing examples

a. The interval between the alto and soprano is more than an octave – this chord is poorly spaced.

b. The interval between the tenor and alto is more than an octave – this chord is also poorly spaced.

c. Tenor, alto and soprano are all closer than an octave, bass and tenor are more than one octave. This chord is spaced correctly.

d. As c, but a less compact sounding chord.

e. Although the tenor and bass are close, the bass is not low-pitched, so this chord will sound fine.

Overlapping & Crossing Parts

Parts should not normally overlap. “Overlap” occurs when the pitches in a chord are out of order. Pay particular attention to the alto and tenor parts as they are on different staves, so overlapping parts are less visually obvious; make sure the alto part is higher than the tenor.

overlapping parts

Here, the tenor F overlaps (is higher than) the alto D – this should be corrected.  

Parts should also not cross each other, as the chords progress.

crossing parts

Here, the tenor D is higher than the alto C which has just sounded – this is an example of crossing parts.  

In fact, in many SATB pieces, such as Bach chorales, overlap does happen, but it is done for a specific reason – for example to create a particular effect. In most exam questions, you will be expected to avoid overlapping parts.

Sharing Notes (Unisons)

It is ok for two adjacent parts to share a note sometimes, but only when there is no better solution.   Here, the soprano and alto share the note E. The texture changes from four-part to three-part harmony when a unison is used, so they must be used in moderation or the texture will sound thin.

SATB unison


The notes must be in the normal range for the voice (or instrument) you are writing for. Don’t forget that tenor voices can easily sing up to around G above middle C (three ledger lines).

vocal ranges

[1] Also known as “voicing”.