Jazz improvisation

Jazz improvisation, which is the making up of new melodic solo lines or accompaniment parts, is a key aspect of jazz. Improvisation is composing on the spot, in which a singer or instrumentalist invents solo melodies and lines over top of a chord progression played by rhythm section instruments (piano, electric guitar, double bass, etc.) and also accompanied by drum kit. While blues, rock and other genres also use improvisation, the improvisation in these non-jazz genres typically is done over relatively simple chord progressions which often stay in one key (or closely related keys using the circle of fifths, such as a song in C Major modulating to G Major).

Along with serious or art music, jazz improvisation is distinguished from other genres use of this approach by the high level of chordal complexity in jazz, often with one or more chord changes per bar, altered chords, extended chords, tritone substitution, unusual chords (e.g., augmented chords), and extensive use of ii-V-I progressions, all of which typically move through multiple keys within a single song. However, since the release of Kind of Blue by Miles Davis, jazz improvisation has also come to be associated with modal harmony and improvisation over static key centers, while the emergence of 1950s-era free jazz has opened up a much wider variety of styles of jazz improvisation, such as "free blowing", in which the soloists improvise freely and ignore the chord changes.

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