Audio: pentatonic harmony (0:08)
pentatonic harmony plays pentatonic harmony by a combo consisting of harmonica, bass and drums. The pentatonic harmony figure shows the score:
Pentatonic harmony uses the five notes in a pentatonic scale.
pentatonic harmony uses the A minor pentatonic scale, one of the most common pentatonic scales. The scale contains the notes, ACDEG. Rearranging them in the sequence, CDEGA, produces the C pentatonic major scale. The two keys, A pentatonic minor and C pentatonic major, are relative keys. This is why these two pentatonic scales are so popular. A further interesting feature of these two scales is that they do not include a semitone or a tritone. The absence of a semitone means that step movement in a melody or a root note is not always possible. The absence of the tritone means that there are none of the issues associated with resolving chords that plague major and minor harmony.
Constructing a pentatonic chord is an interesting exercise. Using the traditional tertian approach produces only two recognisable chords: C major, CEG, shown in bar 2, and A minor, ACE, shown in bar 3. None of the remaining chords are triads, they are all nontertian chords. The chord, GAD, for example, looks like it could be a suspended chord, a Gsus2 or an inverted Dsus4, but it could be interpreted in all sorts of other ways. pentatonic harmony gets round this tricky notation problem by notating the G and A chords in the first bar as major chords, VII and I, when, in reality, they are both power chords, and omit the interval of a third.
Constructing a pentatonic chord progression is a real challenge. For example, the chord progression, C-Gsus2, is bound to occur in C pentatonic major harmony. How can this progression be justified? There is no best answer to this question. Whilst tertian harmony and functional harmony can explain triads, pentatonic harmony contains a mixture of both triads and nontertian chords, and there is no theory for this type of chord mix. A common approach is to treat pentatonic harmony as a stripped down version of major and minor harmony. This approach interprets the nontertian chords as incomplete triads or triads that are modified or altered in some way. An alternative approach is to just go with the flow, accept that pentatonic harmony is an interesting mix of tertian and nontertian harmony, and see where it takes you.
A pentatonic chord progression can be developed in the traditional manner. The root progression, i-iv-V, is available, although the resulting chords will be a mix of complete triads, incomplete triads, suspended chords and power chords. The partial progression, V-I, is also available, but not I-IV-V, and, again, there will be a mixture of chords.
Modulation is the other way to develop a harmony. It is an excellent way to bypass the five note limit of pentatonic harmony. Modulation is shown in the final bar of pentatonic harmony. The key modulates from A pentatonic minor to the parallel key of A pentatonic major, to allow the use of the A major triad, AC#E, although C# could also be treated as a blue note in the key of A minor pentatonic without the need to modulate. The final chord modulates to another key, D major, to allow the use of F# in a D major triad, DF#A. There are hundreds of other pentatonic scales to choose from, in addition to the major and minor pentatonic scales, so modulation is an excellent tool for pentatonic development.
As always, pentatonic throws the melody, rhythm and overall sound into sharp relief. This is illustrated in pentatonic harmony. The melody is only repeated once, in bars one and three. The drums play four different rhythm patterns in succession. Sound effects are used and the drums have been lightly compressed and a small amount of tremolo added to the bass guitar.
Pentatonic harmony is significantly simpler than functional, pop and modal harmony although it is no less interesting to write. It poses some interesting technical challenges, such as which pentatonic scale to use and how to notate chords, and it poses the big conceptual issue: is pentatonic harmony a standalone new approach to harmony or is it a simplified version of existing major and minor harmony?