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Jazz Theory: Modes in Improvisation

The Use of Modes in jazz

When musicians talk about modes in jazz, they often mean the seven modes based on the major scale, however I prefer to think of each mode as a scale in its own right. Having said that, in order to learn the concept, there is nothing wrong with taking a major scale and making each note in turn the tonic of a mode. Modes are used in Modal Jazz, which is not (yet) covered in this course, but knowledge of modes can also sometimes be useful for learning to improvise over chord changes. It is important to realise that this approach should only be used as a preliminary to learning to improvise melodically.

Let’s look at modes in two ways, relative and parallel:

1) Relative

The simplest way to understand relative modes is to start with the major scale of C, but instead of beginning and ending on the note C, begin on each degree of the scale in turn to create a different mode:

jazztheory modes

ex 5a: Relative modes.

2) Parallel

Although the above modes are based on the same notes as the C major scale, they each function as a different key in their own right and the starting note of the mode, not the relative major scale, is the root note. Eg the Dorian mode starting on D (using all the same notes as C major) is a D Dorian not a C Dorian.

Similarly the Dorian mode starting on C (which would use the same notes as Bb major) is a C Dorian, not a Bb Dorian.

If we take one key centre (ie one note) and base different modes on it using that note as the root we get parallel modes. In other words the Dorian mode starting on the note C is parallel to the C major (Ionian mode) and all the other modes starting on C.

parallel modes

ex 5b: Parallel modes

It is important to learn both approaches. Initially it may be easier to think of the 7 modes relatively as above, e.g in relation to a major scale, but a more musical approach is to learn the actual sequence of intervals that make up each mode. In other words a Dorian mode functions purely as a scale by itself, not a relative of the major that starts on the second degree. A good exercise is to write out and learn all the modes in all keys as relative and parallel.

Learn the intervals between each step of the different modes:

( T=Tone, S=Semitone)

Ionian = TTSTTTS (in semitone intervals 2212221)

Dorian = TSTTTST (2122212)

etc.

and learn to sing them using (moveable doh) solfege

Ionian= DO RE MI FA SOL LA TI DO

Dorian= DO RE MAW FA SOL LA TAW DO

Chord/Mode System of Improvising

Improvisers today are often taught a system based entirely on modes and scales, but it is important to realise that although it is necessary for the learning improviser to learn them, scales should ultimately be used to construct musically meaningful melodic lines.

The commonest chord progression is the IIm7-V7-I. The most basic implied scale is the major scale of the I chord, but it may be also useful to think in terms of modes of the major scale in order to visualise the root progression. Take the sequence Dm – G7 – C maj7

There are two ways of approaching this sequence.

1) The Key Centre Method:

Analysis tells us that these chords are diatonic to the key of C, i.e. they all have a key centre of C (C:IIm7-V7-Ima7). A C major scale can be used to improvise over all three chords. This can be useful for the beginner, especially with fast-moving chord changes.

HOWEVER it is often useful for chord notes to fall on strong beats. If you use the C major scale but start the scale on a chord note for each chord you will probably have more success than if you merely use a C major scale indiscriminately over the sequence. This is not easy until you have a thorough grasp of all notes in all chords, hence the alternative approach:

2) The Modal method:

Each chord can be associated with the mode based on its root note.

jazztheory modes

Ex 5c: modes implied by IIm7-V7-I

Note that chord notes fall on the beat. This method also has some drawbacks.

  • You would not always want to start a scale on the root note of a chord.
  • With descending scales the chord notes do not fall on the beat.
  • With fast moving changes it is difficult to think of the modes in time.

In practice it is often useful to cut out one mode in this process: as most V7 chords in mainstream jazz have a preceding IIm7 it can be useful to use the Dorian mode to cover the V7 chord as well.

The key centre method is useful for fast moving chord changes, the modalmethod for slow moving changes when there is more time to think of the modes.

Alternative key centres

In the progression we looked at in ex 2e we found an alternative way of analysing the progression, with a possible key centre of D. If we take a similar progression we can use either the modal or key centre method to choose which scales on which to base an improvisation.

alternative key centre

ex 5d: RN analysis showing alternative key centre.

With the simplified modal method (ignoring Mixolydian) we would think: E Dorian, D Dorian, C major, D Dorian (ex 5e-1)

With the key centre method we would use the alternative key centre and only need to think: D major, C major. (ex 5e-2)

modal method

ex 5e: Modal method and key centre method.

The modal method becomes easier if you treat all minor chords (in a major key) as IIm7 (Dorian). This makes some sense because VIm7 chords are often changed to become secondary dominants (as above -ex 5d), so in many cases minor 7 chords will either be an actual IIm7, or a IIm7 in the new key centre implied by the secondary dominant as with the Em7 above).

Both of these methods can be useful for beginners, as they can make the process of playing over chord changes less daunting, but it is very important to realise that this is only a small step on the way to understanding harmony. In the above example we are thinking of the Em7-A7 as being in D major (key centre method) or E Dorian. The problem is that in this case, although the A7 does not resolve to a tonic, it does not necessarily imply D major, in fact D minor often sounds better for jazz. You will find that a D harmonic minor scale sounds more interesting. You could think in terms of modes of minor scales, however it is far more important to learn the notes of the chords and begin to think about the scale using those notes on the strong beats. This leads to a more musical and melodic approach than the more technical process of thinking in modes for chord changes.

Whenever a cycle of dominant 7ths appears without a preceding IIm7 chord, (e.g. middle 8 of I Got Rhythm sequences), it is either necessary to think of Mixolydian modes (ex 5g) or major scales with a flattened 7th (same thing but easier to learn ):

mixolydian modes

ex 5g: partial cycle of fifths (Mixolydian modes).

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