Harmony

• Foundation for Improvisation
• Harmonic Complexity
• Typical Progressions

This is a preview of the educational program A Jazz Improvisation Almanac which is under development for the Outside Shore Music Online School. Feel free to browse this preview and learn what you can from it. For a more completed product, though, check out the original freely browsable jazz textbook, A Jazz Improvisation Primer.

Foundation for Improvisation

In jazz, harmony is often the foundation of a performance. Harmony is expressed in terms of the chords used to accompany the melody. Aside from the theme, which is often played only at the beginning and end of the performance, the sequence of chords used to accompany the melody may be the only thing that has been prearranged about the performance. This chord progression, also referred to as the chord changes or simply the changes, is also used as a basis for improvisation. In many cases, the musicians read from lead sheets that contain only the melody line and chord symbols. After the melody is played once or twice - often interpreted rather freely - the musicians repeat the original chord progression over and over while improvising new melodies over it. For example, here is an example of a jazz composition with the original melody and accompanying chords:

And here is a new melody improvised over the original harmony:

This progression may be repeated over and over so a soloist can improvise for as long he wants. Not all jazz performances follow this model, but a great many of them do.

Not only are new melodies improvised over the original harmony, but the accompaniment played by the other musicians is usually improvised based on the original chord progression as well. In this example, the melody is the same as the original, but the piano is accompanying differently, based on the same chord changes:

Harmonic Complexity

The harmonies used in modern jazz tend to be richer than those used in other forms of music. Rather than using chords of three or four notes, chords used by jazz musicians often contain five or six different notes, some of which may be considered dissonant at first by ears accustomed to pop or classical music. For example, here is a typical chord progression used in many forms of music:

And here is that same chord progression as it might be interpreted by a jazz musician:

Many of the dissonances in chords used by jazz musicians come from the use of blue notes on top of an ordinary chord used in Western harmony. For example, here are a seventh chord and then the same chord with an added blue note on top:

These extensions and alterations to chords may be improvised, just as melodies are improvised. Furthermore, the melodies - both composed and improvised - often take advantage of these extensions and alterations as well. That is, rather than limiting a melody to notes that belong to the simple three or four note chord, a jazz musician is more likely to use notes from the extended chord. For example, here is a the chord progression given above, with a harmonically simple melody on top, typical of many other styles of music:

And here is that progression with a more harmonically complex melody on top, typical of jazz:

Although the chords used in jazz may be more complex in themselves than those used in other types of music, the way that the chords lead from one to another is not any different from how they function in other styles. In the preceding examples, there is a well-defined key center at any given time, and the various chords all relate to the key center, which may change over the course of a piece. Music with this type of harmony is called tonal. Chords in tonal music resolve in well-defined, even predicatable ways. The progression used above is tonal. Here is a longer example:

There is another style of harmony, called modal, that deemphasises chord resolution. Modal harmony can be used in many different forms of music, but it is especially common in jazz. In a modal jazz composition, the individual chords in a progression often last longer than they do in a tonal composition - perhaps eight measures each instead of one - and they do not lead from one to another so much as they mark separate sections of a composition. Here is an example of a modal chord progression:

Sometimes, a modal jazz composition will take this to the extreme and use just one chord throughout the duration of the composition. On the other hand, a modal jazz composition may contain as many chords as a tonal one. The defining feature of a modal composition is not the number of chords but rather how they relate to each other. In order to illustrate what we mean by this, however, we will have to explain a good deal of the theory of harmony first. We will get to that eventually.

Typical Progressions

There are certain chord progressions that occur especially often in jazz. The most important of these is the blues progression, of which there are many variations. The traditional blues progression is 12 measures long, and is broken into three phrases of 4 measures each which are based, respectively, on the I, IV, and V chords of the key. Here is an example of a blues progression:

As the name suggests, this progression was inherited from the blues. This style is discussed in more detail elsewhere.

Another common pattern in jazz harmony is known as the ii-V-I chord progression. The ii-V-I is rarely the entire chord progression for a composition, but often large portions of the chord progression for a composition can be analyzed in terms of ii-V-I. The essential characteristic of this progression is that the roots of the chords move upward by fourths, or, correspondingly, downward by fifths. Here is an example of a ii-V-I progression:

Another common device in jazz harmony is the vamp - a short repeating sequence of chords. Here is an example of a vamp:

A chord progression does not always repeat unchanged throughout a performance; jazz musicians typically alter chords within the progression to suit the moment. Some compositions contain several distinct chord progressions, perhaps a complex one for the composed melody and a simplified one for the improvised solos, or perhaps a different progression for each soloist. In addition, some musicians occasionally improvise entire chord progressions as well as melodies. This is done mostly by musicians performing unaccompanied, as it would be difficult for a group of musicians to coordinate the improvisation of a chord progression. However, certain simple devices, such as some vamps, are common enough that they are easily recognized by the other musicians if one musician decides to improvise one, and the other musicians are then able to follow along. Also, there are some places, such as the beginnings and ends of performances, where improvised vamps are not unexpected.

Some jazz is atonal - it uses no particular sequence of chords at all to guide the improvisation. Instead, improvisations may be based on the melody alone, or on particular textures, or they may be completely free of preconceived constraints. For example, here is an improvisation that is not based on any particular harmonies:

The term free jazz is often used rather broadly to describe any music that does not have a strict chord progression, although the term is usually applied to music that has no predefined structure at all.

As is the case with melody, it is not always possible characterize a particular chord progression as being jazz harmony. However, jazz musicians, when adapting a song from another style of music to a jazz setting, usually alter the chords in accordance with the descriptions above.

Copyright 2000 Outside Shore Music
Authored by Marc Sabatella

Harmony