A jazz chord is any chord that is commonly used in jazz music. Jazz chords typically use seventh and extended chords, all of which have more than three notes. The chords may or may not have harmonic tension, or dissonance, depending on their structure.
In music theory, which is the study of how harmony and melody are built, the beginning of musical organization is called a scale. A scale is made up of five, seven, or twelve notes. A jazz chord is created using a scale. The most common scales in Western style harmony are the major and minor scales.
Each key has a major scale and three minor scales. The major mode is typically described as happy, powerful, or pleasant. Minor scales are often said to sound sad, mysterious, or exotic. Chords are also described as major and minor chords, although there are also augmented chords and diminished chords. An augmented chord extends the second interval of a major chord, and a diminished chord reduces the second interval, changing the sound dramatically, in both cases.
An interval is the simultaneous playing of one of the scale along with any other note from the scale. The smallest interval is a half-step, which is dissonant, causing musical tension. Three notes played simultaneously form a triad, or a chord.
In major and minor triads, the intervals between each note must be major or minor thirds. For instance, in an A minor chord there should also be a C and an E. That is because C is a minor third from A, and E is a major third from C. A triad is not a jazz chord but it is required to build a jazz chord.
When additional thirds are added to a triad, the resulting harmonies are called extended chords. In the example above, adding a G to A, C, and E would create a seventh chord. It is called a seventh chord because G is the seventh note of the A minor scale.
It is not uncommon for additional thirds to be added to form ninth, 11th, and 13th chords although not all notes in these extended chords are played at once. Usually the fifth is omitted, and in 11th and 13th chords, the ninth. Most extended chords are jazz chords, but the most common jazz chord is the seventh. There are dozens of different kinds of seventh chords. The difference lies in the combination of major, minor, diminished, and augmented intervals of the chord.
Any instrument which can produce two or more notes at once can play jazz chords. The most common instruments that play them are guitar and piano. Musical groups like jazz bands and jazz vocal ensembles use individual voices or instruments to create jazz chords. The notes are played simultaneously so that the chords, can be heard as a single, harmonic sound.