What Is Jazz? Improvisation, Swing and the Music That Came Out of New Orleans

The city had what nowhere else had at once: a black population with African rhythmic traditions and the church music of the spirituals, a Creole community trained in European harmony and instruments, brass bands that played for every parade and funeral, the syncopated piano music called ragtime, and the blues coming up the river from the Delta. In the dance halls and streets of the 1900s these fused into a music played by small groups, a cornet leading, a clarinet weaving above it and a trombone below, over a rhythm section of banjo, tuba or bass and drums, all improvising at once in what was called collective improvisation. The first jazz recording was made in 1917 by a white band from the city, and the musician who turned the ensemble music into an art of solos was Louis Armstrong, whose recordings of the late 1920s established that a single improvising voice, with a sound and a sense of time entirely its own, was what the music was for.

The word jazz musicians use for the rhythmic feel that makes the music itself is swing, and it is easier to hear than to define. Notes written as equal pairs are played long-short, in a lilt somewhere between straight and triplet; the accent falls on the second and fourth beats rather than the first and third; and the players push and pull against the beat rather than sitting on it, so that a swinging band feels as if it is leaning forward. In the 1930s the word named the style: big bands of fifteen or more, arranged for sections of saxophones, trumpets and trombones, playing for dancers, and led by Duke Ellington, Count Basie and Benny Goodman. It was the popular music of America for a decade, the only time jazz has been that, and the small-group improvisers were the soloists who stood up out of the sections.

After the war the music turned away from dancing and towards itself, and each decade produced a style that the last one's players disliked:

• •Bebop, 1940s: Charlie Parker and Dizzy Gillespie, fast tempos, complex chords and long, angular solo lines, played in small clubs for listeners rather than dancers
• •Cool and hard bop, 1950s: Miles Davis's quieter, spacious playing on one side; Art Blakey's gospel- and blues-driven drive on the other
• •Modal jazz, 1959: Davis's Kind of Blue, improvising on scales rather than chord sequences, the best-selling jazz album ever made
• •Free jazz, 1960s: Ornette Coleman and John Coltrane abandoning fixed chords, tempo and sometimes key altogether
• •Fusion, 1970s: Davis again, plugging in electric instruments and rock rhythms
• •Since then: a return to tradition under Wynton Marsalis, and a scattering into every direction at once, taking in hip hop, electronics and the musics of Africa, Cuba, Brazil and India

A standard jazz performance runs on a form. The tune, say a thirty-two-bar song, is played once as written; then the band repeats its chord sequence over and over, in units called choruses, and each soloist takes as many choruses as they want, inventing melodies that fit the harmony as it passes; the rhythm section keeps the form and the time while responding to the soloist; and the tune returns to close. The soloist is not playing randomly. They know the chords, the scales that fit each, the licks of their predecessors and the melodies of a thousand songs, and improvisation is the real-time recombination of all of that, disciplined by years of practice, into something that has not been played before. Listeners follow the form, hear where in the chorus the soloist is, and judge the solo by its invention, its sound, its time and whether it says something. Blues feeling, the bent notes and calls of the older music, runs under nearly all of it.

Jazz is a small share of what is sold, a few percent of music consumption in most countries, and has been since rock and roll displaced it in the 1950s. Its influence is out of proportion to its size: the harmonic language of popular song, the rhythm sections of every genre, the idea of the improvising soloist and the culture of the jam session all came out of it, and it remains the music that other musicians study. It is also the art form that African Americans created and the rest of the world took up, played tonight in Tokyo, Oslo and Johannesburg by people who learned it from records made in New York, and the argument about what counts as jazz and who gets to say so has been going on since the first recording, which is one of the signs that it is alive.

Improvisation looks like pure spontaneity, but jazz musicians learn it in a way closer to learning a language. The traditional method is imitation by ear. A student picks a recorded solo by a player they admire, listens to it over and over, and works out every note on their own instrument, often slowing the recording down to catch the fast passages. Writing it out is called transcribing. The aim is not to reproduce the solo on stage but to absorb its phrases, its timing and its way of moving through the chords, much as a child copies whole phrases before building sentences of their own.

Alongside the records, players rely on lead sheets, a page per tune giving just the melody and the chord symbols, collected in books known as fake books because they let a musician fake a song they have never rehearsed. The jam session is where it is all tested: players sit in with others, trade solos and learn quickly what works in front of an audience. Since the middle of the twentieth century jazz has also been taught in conservatories and universities, which has made the theory more systematic, though most teachers still insist that listening comes first.

Because jazz musicians improvise on chord sequences rather than on melodies, a good sequence can carry many tunes. The most famous comes from George Gershwin's I Got Rhythm, a thirty-two-bar song in four eight-bar sections, three sharing one pattern and a contrasting bridge. Its chords are so well known among players that they are simply called rhythm changes, and hundreds of jazz pieces are built on them, including Charlie Parker's Anthropology and Sonny Rollins's Oleo. A musician who knows rhythm changes and the twelve-bar blues can already find their way through a large share of the standard repertoire.

A new melody written over an existing tune's chords is called a contrafact, and bebop musicians made a habit of it. Donna Lee, from Charlie Parker's group, runs over the chords of the old song Indiana, and Ornithology, credited to Parker and the trumpeter Benny Harris, over How High the Moon. The practice had musical and practical motives. Familiar chords gave players a shared map that needed no rehearsal, while a new melody gave the band something of its own to record. A chord sequence is generally not protected by copyright in the way a melody is, so the new tune could be published as an original composition.

Jazz is music made by improvising over a shared form, usually the chord sequence of a song repeated in choruses, with a rhythmic feel called swing and a foundation in the blues. It grew in New Orleans around 1900 from African American, Creole, brass-band, ragtime and blues traditions, became America's popular music in the swing era, turned inward with bebop, and has since split into every direction, while remaining the music other musicians learn from.