For at least the last two thousand years, the majority of composed art music in the Western world has been made up of two or more simultaneous musical sounds or pitches. The name given to this combination of sounds is harmony.

Most descriptions of harmony focus on Western music but harmony exists in music from other cultures too. In the art music of Southern Asia the underlying harmonic foundation is a drone; a held tone, the pitch of which does not change throughout the piece. Drones have also been common in folk music for centuries, particularly with instruments such as the bagpipes. Combinations of sounds also appear in Indian classical music or rãgas, but whereas in Indian music improvisation takes a major role in the structure, improvisation has not been common in Western classical music since the late 19^th century. Prior to that, improvisation often involved embellishment on written lines rather than the free melodic expression we associate with the word today.

The earliest forms of Western harmony have their origins in church music, when the chants sung by monks were sung in two parts, with a fixed tone, or tones moving parallel to the melody, accompanying the chant. This added depth and colour to the music, where previously a single stark line had existed. This single line chant is called plainchant, and was an ancient monophonic form of music influenced by the Greek modal system.

Harmony has the same function today; when a vocalist is accompanied by a guitar, the right hand of the piano is accompanied by the left hand or when we sing hymns along with an organ, the melody is given depth and interest.

In these instances, the guitar, organ or left hand part of the piano will normally play a combination of several notes at once. A combination of notes played together is called a chord. If you are absolutely new to the idea of harmony and music theory, take a look at this video where the basics are explained right from the start.

And here is a great resource introducing the idea of harmony for children.

Over the centuries, ideas have changed about which chords and combinations of notes make a good harmony. In the 10^th century, the interval of a fourth (two notes, four notes apart) was very popular. Other early harmonies moved in fifths, five notes apart. Parallel fifths, where several chords of pitches five notes apart happen in succession, were also used in folk singing but by the 18^th century parallel fifths were considered undesirable. By the Renaissance, harmony had developed, and the commonest chord was the triad.

A triad is a three-note chord built up in thirds, or where the interval of a fifth is filled out by its central note. It is used both with the notes in their basic order, 1, 3, 5 and in various inversions where the same notes are placed in a different vertical order.

The triad remained the basic harmonic unit in Western music until well into the 20^th century; hence as violinists we practice arpeggios, which are no more than the notes of the triad in each key. It is possible to make a good harmony for many melodies just by using two or three triads, normally the triads of the first, fourth and fifth notes of the scale. These are known as the tonic, subdominant and dominant triads and often written as I, IV and V. More developed melodies sound better with a wider range of harmonies since the way a note is harmonised can change the sense of a piece of music.

Some chords are made up of notes that are dissonant. These are called dissonances, and a dissonance needs to be resolved. Dissonant chords are resolved by consonant chords, which naturally succeed them, creating a smoother sound. The tension generated by dissonant chords can provide a feeling of impetus and energy in music. Wagner used dissonance to great effect in his operas, sometimes moving from one dissonant chord to another, sustaining the resultant tension without resolution, for entire acts which could be as long as two hours of music.

Ideas have altered over the centuries as to which chords and intervals are dissonant and which are consonant. The interval of two notes a semitone, or minor second, apart or their inversion, a major 7^th, forms the strongest dissonance in Western triadic music. The interval of a fourth can be quite dissonant but was not considered so in the 10^th century.

By the early 20^th century, composers were introducing new ideas that replaced the traditional triadic harmony. In modern music, tension and dissonance may be less prepared and less formally structured than in Baroque and Classical music.

Another function of harmony is to punctuate musical phrases. Music has natural stopping places or called cadences, with strong cadences at the end of phrases and weaker ones at other parts in the musical line. Cadences with a clear finality are called perfect cadences and often lead from the dominant or fifth triad to the tonic or first triad, V-I. Imperfect cadences are less final and lead to the dominant.

Harmony is not just chords. As violinists we tend to think melodically or horizontally and harmony can seem quite vertical, but harmony works in the way each successive chord relates to the previous one. It is useful to have an understanding of harmony, particularly if you want to be able to improvise, but also to deepen your understanding of intonation in solo lines and as an ensemble player.

Music theory creates a distinction between harmony and counterpoint. Harmony is understood to occur where there is a melody with accompaniment. Counterpoint is where melodic lines are heard against each other, weaving together so that their notes harmonise. Music using counterpoint is called contrapuntal. Another useful word meaning music made up of several strands is polyphony, from the Greek for many sounds.

Counterpoint was a very important technique for composers in the late Middle Ages and in the Renaissance, when it was used widely in church music.

The concept of imitative counterpoint, a favourite device of composers such as Palestrina, is familiar to anyone who has every sung Three Blind Mice or Frère Jacques as a round.

When music is written, there is an interdependence and integration between vertical and horizontal musical lines. Counterpoint was not succeeded by harmony; harmony developed out of counterpoint and comprises both vertical and horizontal movement. Harmony is a process involving not only the notes which make up a chord, but also the overall flow and progression of chords throughout a composition and the resultant countermelodies which occur.

In Western music, improvisational styles such as jazz have in the past been considered to be inferior to art music, which is pre-composed. Music that exists in oral traditions is separated from notated music, largely because the evolution of harmony has been facilitated by the process of prior composition, which allows for the analysis and study of harmonic techniques.

Jazz and pop harmonies are presented differently and are the basis for improvised melody, rather than being an accompaniment for a pre-composed tune. Have a look at this demonstration of basic jazz harmony. You will see that the chords are shown in the same way, named by their root (bottom note) as IV, V, I and so on, but they are also described by various terms and characters which determine and define the qualities of the chord.  Jazz musicians have to develop a really deep understanding of the notes in each chord and how they operate within the chord in order to be able to improvise with apparent freedom.

If you would like to learn more about harmony, check out our free music theory programme Musition, which comes free with your Violin School subscription.