Improvisation

Professional jazz musicians must be able to make up music spontaneously, playing in any key as required. Some arrangements are notated or have notated sections, but by and large, instrumental solos are improvised. Musicians rely on familiar melodic shapes or 'licks' to help build their improvisations.

Changes

Many jazz pieces use a set pattern of chords or 'changes', such as the 12-bar blues or 32-bar song form (AABA). Players are often expected to know the most familiar tunes, or 'standards' and be able to play them in any key.

Tone and timbre

Jazz instrumentalists use a variety of ways to alter the sound of a note. Vibrato can be fast or slow. A rough or breathy tone can be used deliberately. There are different types of mutes to vary the sound of brass instruments. Variety of attack and decay - how notes begin and end - is also an important characteristic of jazz.

Blues intonation

A blue note is usually the flattened 3rd, 5th or 7th of the scale. Because the scale derives from African vocal music, the tuning of these notes is often microtonal (you'll hear this on guitars and wind instruments) and is often emphasised with a bend or a growl.

Walking bass

Early jazz bass parts were frequently march-like, based around tonic and dominant notes. The walking bass (on a plucked double bass) emerged in the 1930s and 1940s. The bass line keeps the beat, but it also rises and falls, improvising around chords in a combination of scale and broken-chord patterns. It has a sense of shape and direction.

Rhythm section

This is usually made up of piano, guitar, double bass and drums. Early jazz often used banjo, with a tuba for the bass. Later jazz (e.g. Miles Davis' later works) has electric alternatives for acoustic instruments: bass guitar, electric guitars and keyboards.

Front line

The instruments playing the melody line. New Orleans style (also known as 'Dixieland') featured trumpet (or cornet), clarinet and trombone. The big bands used saxophones as the basis of the reed section and for solos.

Swing

The jazz style of the 1930s and 1940s is often known as 'swing'. However, swing is also used to describe the rhythmic feeling of the jazz music from this era. Ragtime was known for using syncopation. Jazz gave the straight eighth-notes of ragtime (eight even quavers in a four-beat bar) a lilting feeling by lengthening the first quaver of every pair, and shortening the following note. Anticipating or delaying beats against the steady beat of the rhythm section adds to the feeling of swing.