An Introduction to Jazz Theory

For many people Jazz theory presents an impenetrable barrier which only the most dedicated or gifted can breach. Certainly some of the chord progressions which Jazz musicians are expected to improvise over can test even an advanced practitioner of the style; not least because of the tempos. While this article does not claim to improve your improvisational or performance abilities, it will I hope, introduce you to the language of Jazz.

Because Jazz music spans over a century of styles and sub-genres, the theory which I will discuss below is broadly based on concepts which underpin most of these styles. Much Jazz theory is drawn from existing usage in Classical or other styles of music and I will connect these where applicable. Before we go on, however, it is essential that you remember this fact:

Jazz essentially uses the same 12 notes that Pop, Rock, Classical, Blues and most all other Western music uses. It is how these notes are stacked, grouped and performed which gives Jazz its sound.

With this in mind, let us begin.




One of the first things you notice when listening to, or performing, Jazz is the swing rhythm. While its use may not be prominent in all styles of Jazz, most people would consider it one of the defining characteristics of the genre.

Swing rhythm can be characterised by a triplet feel applied to straight eighth-notes.


While this definition may be an oversimplification of the resulting sound, it should, when coupled with dedicated listening to the genre, give an approximation of the swing ‘feel’.





Another characteristic of Jazz as a genre is the use of improvisation. While improvisation has been used for centuries in many other styles of music, the ability to improvise is one of the basic requirements of Jazz practitioners. A good knowledge of the genre’s melodic and harmonic elements, along with an understanding of its forms and phrasing provide the Jazz musician with the necessary ‘tools’ to perform. The close interplay between all improvising musicians in a Jazz combo, allows for unexpected musical developments to occur, and it is the performers’ knowledge of these ‘tools’ which allows them to navigate these developments.

The Blues:


The Blues underpins many elements of Jazz, not only in relation to Jazz’s harmonic and melodic language but also as a foundation for many of its song forms.

An example of the Blue’s influence on form is the tune, Now’s the Time by Charlie Parker (the harmonic structure of the first 12 bars are shown below).

Now's the Time

Parker has simply used the standard 12-bar blues as a basis but has added several ‘extra’ chords to this foundation. The second half of the tune consists of the same 12 bars but is harmonically simpler than the first 12 as it is used to solo over (often the chord changes used for soloing over are a ‘stripped down’ version of the first section). A standard 12-bar blues is shown below for comparison.

Quick change Blues



In Jazz, if tunes are not newly composed, many are taken from musicals, films and songs – usually these songs are from the so-called Great American songbook. Often these tunes will be adapted or reworked for use in various Jazz settings. Many tunes from earlier Jazz greats are now considered Jazz Standards, such as the Parker work discussed above, however, newer tunes are also constantly being added to this ever-expanding repertoire.

In Jazz jargon the tune is called the head and is typically played before the solos begin, the head is often played again to complete the tune after all solos have been taken.




Another feature of Jazz, which is characteristic of the style, is the use of chromaticism. The amount of chromaticism will vary and depends on the performers’ personal style and on the era of Jazz you are listening to.

Many Jazz melodies make use of chromatic embellishments which include: chromatic upper and lower neighbour notes, chromatic passing notes, and appoggiaturas.


Harmonically, chromaticism is present through the use of half-step approach chords, secondary and passing chords.

Chroma Chords

It is also found in the altered extensions of dominant harmony (see next section).

The use of chromaticism is not new in music and has been used, in varying degrees, for centuries. In particular, the use of chromatic melodic embellishments is often found, as can be seen in the opening of Fugue 24 from Book One of J. S. Bach’s The Well Tempered Clavier.


In this example, Bach precedes many of the notes of the underlying progression with appoggiaturas which colour the tonal framework. Harmonic chromaticism is also extensively found in other styles of music, it can be found ‘locally’ through the use of secondary and passing chords, or can be broadly applied through tonicisation.


Extended Harmony:


Jazz makes considerable use of extended chords. Often the extensions are chromatically altered – this is especially true of dominant harmony but can also be found in other types of extended chords. At the very least, all Jazz harmony typically includes the seventh, which produces the following diatonic seventh chords in a major key.

Harmonised 7ths

Other types of extended chords commonly used in Jazz include the 9th, 11th and 13th chords. These extensions may be altered to create chords such as the following.

Altered Dom

The sharp and flat extensions of these chords may be found in the melody played over the chord, or they may be added at the discretion of the composer and/or performer to ‘colour’ the chord.


II – V – I progressions:


A common structural feature of many Jazz tunes is the ii – V – I progression, which in music theory terms outlines a perfect Cadence (V – I). Along with forming the harmonic foundation of complete tunes, or parts of tunes, ii – V – I progressions are also used as a basis for soloing – and are sometimes performed even when they are not written in the score.

Consider the following


When confronted with the four bars of G seventh chord in the top progression, rather than simply outlining the G seventh harmony in their solo, a Jazz musician may choose instead to imply the two sets of ii – V – I progressions in the second progression. The chords in the first two bars of the second progression (D minor seventh – G seventh) outline the diatonic ii – V progression in C major while the chords in the following two bars (A flat minor seventh – D flat seventh) outline a ii – V progression which, through a tritone substitution, resolves by a semitone to the C major chord (D flat – C) (tritone substitutions will be discussed in a later article).

II – V – I progressions have also been used extensively in many other styles of music. As previously mentioned, harmonically, these progressions form a perfect cadence and are therefore one of the cornerstones of all tonal music. Melodically, they may also be found in many styles of music as can be seen in the following excerpt from Niccolo Paganini’s Caprice No. 16 in G Minor.


Here, the tonic G minor chord in bar 4 is altered to form the dominant of chord iv, bar 5. Chord iv can also be heard as chord ii of a ii – V – I (Cm – F7 – B flat) progression which ends on chord III of G minor, in bar 6.




Jazz incorporates many modes within its panoply of techniques and structures. While an in-depth discussion of their many uses is beyond the scope of the present article I will outline some of the more common types, and their application.


Minor Chords:


A common mode to use over minor chords is the Dorian mode, which is the second mode of the major scale – in the key of C major the Dorian mode begins on D. To solo over a D minor chord, therefore, you could use the D Dorian mode, while over an F minor chord you could use the F Dorian mode. Another common mode to use over a minor chord is the Aeolian mode (the sixth mode of a major scale). The Aeolian mode is also the relative minor key: over an A minor chord you could solo using the A minor scale; the A Aeolian mode.


Major Chords:


Over major chords a common mode to use is the Lydian mode, which is the fourth mode of the major scale – in the key of C major the Lydian mode begins on F. To solo over an F major chord, therefore, you could use the F Lydian mode, while over an A major chord you could use the A Lydian mode.Another common mode to use over a major chord is the Ionian mode (the first mode of a major scale). The Ionian mode is simply the major scale: over a C major chord you could solo using the C major scale; the C Ionian mode.

Dominant Chords:


Over dominant chords a common mode to use is the Mixolydian mode, which is the fifth mode of the major scale – in the key of C major the Mixolydian mode begins on G. To solo over a G dominant chord, therefore, you could use the G Mixolydian mode, over an E dominant chord you could use the E Mixolydian mode.

The use of modes in other styles of music has a long history. Medieval and Renaissance music was essentially based on the modes of the modern major scale and these modes have continued to be used, along with others, up to the present day.


Fundamentally, Jazz theory is not too different from the Classical theory on which most Western music is based. This of course does not preclude the influence which music from other cultures has had, and continues to have, on the Jazz genre.

Hopefully, this introduction has given you an insight into Jazz and has encouraged you to gain more of an understanding of its language. However, as with learning any language, only through constant repetition, immersion and practise will the greatest understanding be gained.

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