The Jaco Pastorius etude in Figure 13-5 opens up one additional can of worms: the diminished scale. Specifically, this etude uses a diminished scale on the altered V chord in measures five and six. A diminished scale is an exotic and snaky mode. These scales are made up of alternating whole and half steps. Figure 13-6 shows three versions of this scale.

Figure 13-6.

Three diminished scales

W = Whole Step H = Half Step

Notice how all three of the diminished scales in Figure 13-6 follow the whole-half intervallic model. For this reason, these scales are often called whole-half scales. You will usually hear jazz musicians using this term.

Because of intervallic symmetry, there are only three diminished scales. Other diminished scales, with varying names, can be formed by starting on a different note of one of the three basic diminished scales illustrated in Figure 13-6. Here, you see C, C-sharp, and D diminished scales. If you were to keep building scales chromatically, the next scale would be D-sharp diminished. However, if you remember that D-sharp is the same as E-flat, all you need to do is begin on the third scale degree of the C diminished scale. If you do this, you will have the D-sharp (or E-flat) diminished scale. Again, the symmetrical nature of these scales makes this all possible.

How do you use the diminished scale? As you might imagine, diminished scales can be used on diminished chords. For example, a C diminished scale can be used on a C diminished chord. However, in jazz they are mainly used over dominant seven/flat nine chords and dominant seven/ sharp nine chords. For instance, you saw it used in measures five and six of “Jaco Lives.” In short, you can use a diminished scale on these types of altered dominant chords because diminished chords are really the same as dominant seven chords with a flat nine. In this case, simply use the half-whole version of the diminished scale beginning on the note name of the flat/sharp nine chord (as in using G half-whole over a G7 9 chord).