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Two or more notes sounding together are known as a chord.

Triads

A triad is a chord of three notes. For example, C - E - G is the C major triad. C is the root note, E is the third - an interval of a third above the root - and G is the fifth - an interval of a fifth above the root.

Dominant and subdominant

In any major key, the chords built on the first, fourth and fifth degrees of the scale are all major. In the key of C, these are the chords of C, F and G. They are also sometimes called I, IV and V (for first, fourth and fifth in Roman numerals), or primary triads.

The chord built on the first note of the scale, I, is called the tonic. The chord built on the fourth, IV, is called the subdominant and the V is called the dominant.

All the chords built on other notes in the scale of C are minor, except chord VII - the notes B – D – F, which is diminished.

Sevenths

When a seventh is added to a chord this is known as a seventh chord. The dominant seventh of a V chord can be shown by the symbol V7.

For example, G7 is made by taking the major triad of G (G - B - D) and adding an F (G - B - D - F).

Types of chord

• A concord is a chord where all the notes seem to 'agree' with each other. It feels at rest and complete in itself.
• A discord is a chord where some notes seem to 'disagree' or clash giving an unsettled feel.
• Diatonic harmony uses notes that belong to the key.
• Chromatic harmony uses notes from outside the key to give the chords more 'colour'.

Cadences

A cadence is formed by two chords at the end of a passage of music.

• Perfect cadences sound as though the music has come to an end. A perfect cadence is formed by the chords V - I.
• Interrupted cadences are 'surprise' cadences. You think you're going to hear a perfect cadence, but you get a minor chord instead.
• Imperfect cadences sound unfinished. They sound as though they want to carry on to complete the music properly. An imperfect cadence ends on chord V.
• Plagal cadences sound finished. Plagal cadences are often used at the end of hymns and sung to “Amen”. A plagal cadence is formed by the chords IV - I.

Sometimes the final cadence of a piece in a minor key ends with a major chord instead of the expected minor. This effect is known as a Tierce de Picardie.

The video shows examples of different types of cadence.

Tonality

The character of a piece of music is related to its key centre or tonality:

• tonal music is in a major or minor key
• atonal music is not related to a tonic note and therefore has no sense of key
• modal music is in a mode

Two common modes are the Dorian mode and the Mixolydian mode. Modes are often found in folk music, pop music and jazz.

Modulation

When a piece of music changes key, it is said to modulate. It is most likely to modulate to a closely related key.

The keys most closely related to the tonic are the dominant, the subdominant or the relative minor or major keys.

Drone, pedal and ground bass

• A drone is a held or repeated chord, usually a bare fifth, throughout a passage of music.
• A pedal is a single note that is held on or repeated in, the bass. An inverted pedal note is a sustained or repeated note in a high register.

The chords above the bass may change, but the bass note stays the same.

In the example, the pedal note is C, which you can see in the bass part.

“Ground bass” is the term used in Baroque music where a bass part is repeated throughout the piece. Whereas an ostinato pattern might be very short, a ground bass can last many bars before it is repeated.