Avoiding Parallel Fifths

A quick recap: the basic rules of motion

Before we dig in, here are the basic rules of harmonic motion that the full course sets out when it first harmonises a cadence. We keep them as straightforward as possible, and they are the result of many centuries of composers deciding what makes harmony sound best.

Parallel Fifths and Octaves

Here we are going to look at the problem of parallel 5ths and octaves in more detail. The following examples show parallel fifths and parallel octaves. In the classical and baroque period they were strongly discouraged. They are still counted as parallels even if they are moving in opposite direction, as you will see from this example.

If all the intervals move in the same direction, with the chord in the same inversions, you will get lots of parallel intervals.

The reason this is frowned upon in some circles is because it destroys the independence of the individual voices and makes them sound more like block chords. Remember back at the start we talked about writing in a different way? That rolling river of sound you get when listening to well written string or vocal music, that is the result of the harmony consisting of four independent lines of music. Once you lock each chord into the same shape, that effect is destroyed and locking the fifths and octaves from one chord to the next is really the nail in the coffin of your beautiful harmonic writing.

The interval of the fifth and octave is very powerful, as it is an important harmonic of each and every fundamental note. Therefore, the resonant sound of the fifth can overpower everything else and spoil that constantly evolving river of sound effect we are aiming at.

However, lots of composers use consecutive fifths all the time – where would the Pink Panther be if Henry Mancini had listened to his composition teacher? Aaron Copland equally uses parallel fifths all the time, quite consciously, to evoke the sound of "traditional Americana".

Here are two ways of harmonising the same phrase, the first with parallel fifths and octaves and the second without. See if you can hear the difference.

In the first example above, there are parallel fifths between the alto and tenor parts in the first whole bar. At first glance this would appear to be the best way to harmonise these chords as the individual parts flow to the nearest harmony note with ease. However, if we swap the inner parts, this eliminates the parallel fifths as in the second version. There are also parallel octaves between the soprano and bass parts in the second bar of the first version. However, by changing the inversion of the chord so that the bass rises rather than moving to the root, this parallel can also be removed. This would mean that both the bass and tenor are doubling the third of the chord, with no fifth. As the bass is now on the third, the tenor can move to the fifth instead.

Parallels are most difficult to avoid when you are going from two adjacent chords like from IV to V. One trick is to ensure that the bass rises as the other three parts fall, or vice versa.

Let's look at some problem examples in 3-part harmony first of all.

Avoiding parallels with 3 parts

There are parallel fifths between the bass and soprano and you will see that all the parts are moving in the same direction to the nearest harmony note of the next chord. This is a common problem with consecutive chords in the same position i.e. both in root position or both in first inversion.

However, if we were to swap the upper two parts around on the second chord, the soprano would fall, thus no longer forming parallel fifths with the bass. However, this does mean that the alto part has a jump of a fifth and sometimes you don't want to change your melody.

Another solution would be to use our first inversion. The parallel can be avoided by using a first inversion chord on chord IV. This also means that all the parts move smoothly to the next chord, so this is a good solution.

We could try using a first inversion of the chord V instead, but this would not be as good.

This is because the bass would have to jump an augmented fourth. This is a difficult interval to pitch and therefore to be avoided. You can see this in the example above.

There are many more variations that you could use to avoid parallels in this case, including second inversion chords, which we will come on to in the next unit.

Avoiding parallels with 4 parts

Now let's look at the problem of parallels in 4-part harmony. This example has parallel fifths between the soprano and alto as well as parallel octaves between alto and bass.

The first option is to change the upper parts around.

If you look at the example above, you will see that the bass rises while the other parts fall.

However, we could use an inversion to avoid the problem, by creating a different layout of the chord, therefore removing the parallels.

And that's it! These early exercises in harmony don't seem much like "real music," but I'm afraid we need to get this bit cracked before we can move on to more interesting and therefore complicated arrangements.