A2 | Triad

What is a triad?

A triad is three notes played together. Each triad has an interval of a 3rd between each note.

Look at the scale below. You’ll see that notes have been added above notes 1, 4 and 5 of the scale to create chords.

  1. These chords are called primary chords.
  2. As the notes 1, 4 and 5 are the ones with chords built on them, the three chords are also called chords I, IV and V, commonly written using Roman numerals.
  3. These are the three main chords in any major key.

Using the primary triads

You can create songs using only these three chords. Everyone knows the carol Silent Night. Silent Night was originally composed in 1818 by Franz Xavier Gruber.

Listen to the melody and chords used.

Click on this link to see the melody and the chords used.

Further listening

Rhedeg i Baris (Yr Anhrefn/Candelas) – which also uses the three primary chords.


How do you decide which chord to use with the notes of a melody?

  1. Form the key’s three primary chords on notes 1, 4 and 5.
  2. Looking at the notes in the melody, try to pair or match a note from the melody with one of three notes in the chord. This is called harmonising.

Click on this link to add chords to a well-known melody by the composer Charpentier. The key is C major, therefore you need to remember once again what the three primary chords are.

First of all, listen to the melody: