Chords and sequences of chords are mostly used in modern West African and Oceanic music, Western classical music, and Western popular music ; yet, they are absent from the music of many other parts of the world.
In tonal Western classical music (music with a tonic key or “home key”), the most frequently encountered chords are triads, so called because they consist of three distinct notes: the
root note, and intervals of a third and a
fifth above the root note. Chords with more than three notes include added tone chords , extended chords and
tone clusters, which are used in
contemporary classical music , jazz and other genres.
Chords can be represented in various ways. The most common notation systems are:
- Plain staff notation, used in classical music
- Roman numerals , commonly used in harmonic analysis to denote the scale step on which the chord is built.
- Figured bass , much used in the Baroque era, uses numbers added to a bass line written on a
staff, to enable keyboard players to improvise chords with the right hand while playing the bass with their left. - Chord letters, sometimes used in modern musicology, to denote chord root and quality .
- Various chord names and symbols used in popular music lead sheets, fake books , and chord charts, to quickly lay out the harmonic ground plan of a piece so that the musician may
improvise, jam , or vamp on it.
