The final section of the intervals lessons deals with how they can be played on guitar. Harmonic intervals are always present within chords, of course, but there are some distinct musical effects that are obtained by playing the same types of (usually consonant) harmonic intervals in succession.
FIFTHS AND FOURTHS
Perfect fifths and
fourths were being used long before the first chords made an appearance. They were the first attempts at harmony in western music, and began to be used as standard in the middle ages by monks singing Gregorian chant. The haunting, hollow sound that we associate with this type of singing (called
organum) is purely as a result of using only perfect fifths and fourths.
Nowadays,
fifths and
fourths are most commonly heard in rock music as
power chords, played on electric guitars usually with overdrive. Despite the name, power chords aren't really chords, they're intervals consisting of perfect fifths or fourths (with or without octave doubling). Power chords are unique because their
perfect consonance means they can withstand high levels of distortion. Full chords or other intervals can sound unacceptably discordant when distorted at high amplification levels. Well-known examples of power chord sequences in songs are:
Smoke on the water - Deep Purple
Smells like teen spirit - Nirvana
My Generation - The Who
THIRDS
Thirds generally add a pleasing harmony to a melody.
Depending on the key and melody notes, the
thirds will vary between
major and
minor forms in accordance with the key. Some guitarists practise
thirds in scale form. That means playing a scale but accompanying every note with another scale note a third above, For example:
The scale of C major harmonised by major and minor thirds above.
E F G A B C D E
C D E F G A B C
E||--0----1----3----5----|--7-----8----10----12----||
B||--1----3----5----6----|--8----10----12----13----||
G||----------------------|-------------------------||
D||----------------------|-------------------------||
A||----------------------|-------------------------||
E||----------------------|-------------------------||
They are often heard in fingerstyle and classical guitar playing as compound intervals, i.e. a
third plus an
octave. In this form, they can make a very effective
bass and melody, as in the example below. Playing intervals is sometimes preferred to using chords because of their lighter sound. This also means they can change on every note. Chords, by contrast, don't sound so good if they are constantly being changed on every note.
SIXTHS
Sequences of
sixths are very common in
blues and blues-influenced music. They are really
inverted thirds as was explained in the previous lesson (
inverted intervals) and the above scale can also be practised with the same notes but inverted. so that the harmony notes lie below the main scale notes, rather than above (as thirds). As with thirds, the key will determine whether any sixth in the sequence will be major or minor. As the notes of sixths aren't played on adjacent strings, they are mostly played fingerstyle. They can't be played with a pick unless a finger is brought in to pick the upper notes while the pick is used on the lower notes, in the technique known as 'hybrid picking'.
The scale of C major harmonised by major and minor sixths below.
C D E F G A B C
E F G A B C D E
E||------------0----1----|--3----5----7----8----||
B||--1----3--------------|----------------------||
G||------------0----2----|--4----5----7----9----||
D||--2----3--------------|----------------------||
A||----------------------|----------------------||
E||----------------------|----------------------||
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In conclusion, we've seen that intervals are highly varied and very useful in both the theory and practice of music. Once you understand them completely, many doors to a more advanced understanding of the complex structures of music will be opened to you.
Audio examples
1. Compound thirds as bass and melody in a typical simple classical style. Notice how the
lightness of intervals means they can change on every note to good effect - unlike chords, which usually need to sustain longer.
2. Sixths in a typical blues intro. At first the notes are played separately, then together as true
harmonic intervals.