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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.
Jazz improvisation can be divided into soloing and accompaniment.
When soloing (also called "blowing"), a performer (instrumentalist or singer) creates a new melodic line to fit a song or tune's chord progression. During a solo, the performer who is playing the solo is the main focus of the audience's attention. The other members of the group typically accompany the solo, except for some drum solos or bass solos in which the entire band may stop while the drummer or bassist performs. When a singer improvises a new melody over chord changes, it is called "scat singing". When singers are scat-singing, they typically use made-up syllables ("doo-bie-bo-ba"), rather than use the lyrics of the song. Soloing is often associated with instrumental or vocal virtuosity; while many artists do use advanced techniques in their solos, this is not always done. For example, some 1940s and 1950s-era bass solos consist of the bassist playing a walking bassline.
There are a number of approaches to improvising jazz solos. During the Swing and big band era, performers typically improvised solos by ear, by using riffs and variations on the tune's existing melody. During the Bebop era in the 1940s, jazz composers began writing much more complex chord progressions. As a result, in the Bebop era, soloists like sax player Charlie Parker began soloing using the scales and arpeggios associated with the chords in the chord progression.
In jazz, when one instrumentalist or singer is doing a solo, the other ensemble members play accompaniment parts. While fully written-out accompaniment parts are used in large jazz ensembles, such as big bands, in small groups (e.g., jazz quartet, piano trio, organ trio, etc.), the rhythm section members typically improvise their accompaniment parts, an activity called "comping". In jazz, the instruments in the rhythm section depend on the type of group, but they usually include a bass instrument (double bass, electric bass), one or more instruments capable of playing chords (e.g., piano, electric guitar) and drum kit. Some ensembles may use different instruments in these roles. For example, an 1920s-style Dixieland jazz band may use tuba as a bass instrument and banjo as the chordal instrument. A 1980s-era jazz-rock fusion band may use synth bass for the bassline and a synthesizer for chords. Some bands add one or more percussionists.
In small groups, the rhythm section members typically improvise their accompaniment parts. Bass instrument players improvise a bassline using the chord progression of the key as a guide. Common styles of bass comping parts include a walking bassline for 1920s-1950s jazz; rock-style ostinato riffs for jazz-rock fusion; and Latin basslines for Latin jazz. Improvised basslines typically outline the harmony of each chord by playing the root, third, seventh and fifth of each chord, and playing any other notes that the composer has requested in the chord (e.g., if the chord chart indicates a sixth chord on the tonic in C Major, the bassist might include the sixth degree of the C Major scale, an "A" note, in her/his bassline).
The chordal instrument players improvise chords based on the chord progression. Chordal instrument players use jazz chord voicings that are different from those used in popular music and Classical music from the Common Practice Period. For example, if a pop musician or Baroque music era (ca. 1600-1750) were asked to play a dominant seventh chord in the key of C Major, they would probably play a root position chord named G7 (or "G dominant seventh"), which consists of the notes G, B, D and F, which are the root, third, fifth and flat seventh of the G chord. A post-Bebop era jazz player who was asked to play a dominant seventh chord in the key of C Major might play an altered dominant chord built on G. An altered dominant contains flattened or sharpened "extensions" in addition to the basic elements of the chord. As well, in jazz, chordal musicians often omit the root, as this role is given to the bass player. The fifth of the chord is often omitted as well, if it is a perfect fifth above the root (as is the case in regular major chords and minor chords.
The altered extensions played by a jazz guitarist or jazz pianist on an altered dominant chord on G might include (at the discretion of the performer) a flatted ninth Ab (a ninth scale degree flattened by one semitone); a sharp eleventh C# (an eleventh scale degree raised by one semitone) and a flattened thirteenth Eb (a thirteenth scale degree lowered by one semitone). If the chordal playing musician were to omit the root and fifth of the dominant seventh chord (the G and D) and keep the third (B) and flatted seventh (F), and add the altered tones just listed (Ab, C# and Eb), the resulting chord would be the pitches B, C#, Eb, F, Ab, which is a much different-sounding chord than the standard G7 played by a pop musician (G, B, D, F). In Classical harmony and in pop music, chord voicings often double the root to emphasize the foundation of the chord progression.
From the Dixieland era through to the swing music era, many solo performers improvised by varying and embellishing the existing melody of a song and by "playing by ear" over the chord changes using well-known riffs. While this approach worked well during these musical eras, given that the chord progressions were simpler and used less modulation to unusual keys, with the development of Bebop in the 1940s, the embellishment and "playing by ear" approach was no longer enough.
While Dixieland and swing music were both designed for the enjoyment of listeners, and in the case of swing, for dancers, bebop was more of a "musician's music", designed for listening. While there are important bebop tunes with vocals and lyrics, many of the most important bebop tunes are instrumentals. Bebop used complex chord progressions, unusual altered chords and extended chords, and extensive modulations, including to remote keys that are not closely related to the tonic key (the "main" key or "home key" of a song). Whereas Dixieland and swing tunes might have one chord change every two bars with some sections with one chord change per bar, bebop tunes often had two chord changes per bar with many changing key every four bars. In addition, since Bebop was written for listening rather than dancing, the tempi were not constrained by the need for danceability; as a result, bebop tunes were often faster than those of the swing era.
With bebop's complex tunes and chords and fast tempi, melodic embellishments and "playing by ear" were no longer sufficient to enable performers to improvise effectively. Leading bebop soloists such as saxophone player Charlie Parker began to solo by using scales associated with the chords, including altered extensions such as flatted ninths, sharp elevenths and flatted thirteenths, and by using the chord tones and themselves as a framework for the creation of chromatic improvisation.
Modes are all the different musical scales and may be thought of as being derived from various chords. Musicians can use these "modes" as a pool of available notes. For example, if a musician comes across a C7 chord in a tune, the mode to play over this chord is a "C mixolydian" scale.
These are various chord derivations that help musicians know which chord is associated with a certain scale or mode:
One of the key concepts of improvisation in Bebop and subsequent jazz eras is targeting, a technique used by sax player and composer Charlie Parker. The main idea of targeting in solo improvisation is "landing" on the tones of a chord. A chord is built up of a root (1st) and the notes a 3rd, 5th, 7th, 9th, 11th and 13th above the root in the scale. There are a number of ways to target a chord tone. The first is by ascending or descending chromatic approach (chromatic targeting). This means playing the note a semitone above or below one of the chord tones. In the key of C, the notes in the tonic chord are C(1st or root of chord), E(3rd), G(5th), and B(7th). So by playing an E flat at the end of a line then resolving (moving up a semitone) to an E, this would be one basic example of targeting and would be targeting the third of the chord (E♮). This may be used with any factor of any type of chord, but rhythm is played so that the chord tones fall on the downbeats.
In Bebop melodic improvisation, targeting often focused on the 9th, 11th and 13th of the chord - the 'color tones' - before resolving later in the phrase to a 7th chord tone. In bebop the 9th, 11th and 13th notes were often altered by adding sharps or flats to these notes. Ninths could be flatted or sharpened. Elevenths were typically played sharpened. Thirteenths were often played flat. Enclosure is the use of scale tone(s) above the targeted note and chromatic tone(s) below, or scale tone(s) below and chromatic tone(s) above.
Another technique in jazz improvisation, used by Charlie Parker and most great jazz soloists, is known as the "three to flat nine" (these numbers refer to degrees of the scale above the root note of a given chord in a chord progression). This is a very bebop approach to improvisation, similar to targeting. This technique can be used over any dominant chord that can be treated as a flat nine (b9) dominant chord. It entails moving from the third of a dominant chord, to the flat nine of a dominant chord, by skipping directly to the ninth, or by a diminished arpeggio (ascending: 3rd, 5th 7th, ♭9th). The chord often resolves to a major chord a perfect fourth away. For example, the third of a G7 chord is B, while the flat ninth is A♭. The chord resolves to C and the note A♭ leads to G.
Pentatonic scales are also commonly used in jazz improvisation, drawing perhaps from their use in the blues. Saxophone player John Coltrane used pentatonics extensively. Most scales are made up of seven notes: (in the key of C – the major scale) C D E F G A B). The major pentatonic scale comprises only five notes of the major scale (C pentatonic scale is C D E G A), whereas the minor pentatonic scale comprises the five notes (C E♭ F G B♭). Pentatonics are useful in pattern form and that is how they are usually played. One pattern using the pentatonic scale could be 3 6 5 2 3 5 (in C: E A G D E G). Pentatonic scales also become popular in rock music, jazz fusion and electric blues.
Lines (also known as licks) are pre-planned ideas the artist plays over and over during an improvised solo. Lines can be obtained by listening to jazz records and transcribing what the professionals play during their solos. Transcribing is putting what you hear in a record onto music paper. Cells are short musical ideas. They are basically the same things as lines, but they are shorter.
Phrasing is a very important part of jazz players' set of improvisational skills. Instead of just playing a sequence of scale and chord notes that would work based on the chords, harmony, etc., the player builds an idea based on a melodic motif or a rhythmic motif. The player in effect extemporizes a new melody for a tune's chord progression. Alto saxophonist Charlie Parker, who is considered to be an exemplar of jazz improvisation, paid special attention to the beginning and ending of his solos where he placed signature patterns that he developed over the years. The middle part of his solos used more extemporaneous material that was created in the moment. This shows a developed style of musical phrasing where the shape of the melody has a logical conclusion. With his strong beginning, Parker was free to create solos that demonstrated musical phrasing, and led to a logical and memorable conclusion. Examples of this motif-based approach in a compositional context are found in classical music. In Beethoven's fifth symphony, the first rhythmic and melodic idea is played again with many variations.
Eugene W. Holland has proposed jazz improvisation as a model for social and economic relations in general. Edward W. Sarath has proposed jazz improvisation as a model for change in music, education, and society.