This guitar lesson explains how to use diminished scales in improvisation, and includes an example guitar solo plus a backing track so you can solo with diminished scales yourself. For more information on diminished scales, see this page: Diminished Scale Guitar. Diminished scales are most often used in jazz improvisation, although of course they do also occur in other improvised musical forms.
Diminished Scale Theory
Diminished scales naturally fit very well when played over diminished chords with the same note name (e.g. a G diminished scale can be played over a G diminished chord). Because each diminished scale is in effect four scales in one, either B flat, D flat or E diminished scales can also be played over a G diminished chord. Each of these scales contains exactly the same notes.
However, the reason diminished scales are used so frequently in jazz improvisation is because they produce tensions when played over dominant seventh chords. Put simply, tensions are notes which create interesting melodic effects, and playing tensions gives phrases a jazz sound. To use a diminished scale over a seventh chord, the diminished scale with a root one semitone higher than the root of the seventh chord is used (e.g. an A flat diminished scale over a G7 chord).
A G7 chord contains the following notes: G, B, D, F
An Ab diminished scale contains the following notes: Ab, Bb, B, Db, D, E, F, G
The Ab creates the flattened nine tension, the Bb the sharp nine and the Db is the flat five of a G seventh chord.
Example Solo Using Diminished Scale
This example solo highlights the interesting sounds that can be produced by soloing with a diminished scale over a dominant seventh chord. The example is played over the following chord sequence:
An F sharp diminished scale is used over the F sharp diminished chord, and a C sharp diminished scale is played over the C7 chord in the fourth bar (the 'alt' means that the chord could potentially contain altered notes such as a sharp or flat five or nine)
Example Of Improvisation With Diminished Scale
Diminished Scale Backing Track
Experiment by incorporating the diminished scale in your own solos. You can use the shapes shown here: Diminished Scale Guitar. The following backing track uses the same chord sequence as the above example. The diminished scale can sound quite odd at first, but persevere, and you'll get a feel for when the tensions it produces will work. You'll also start to notice it being used in much contemporary jazz.