What's wrong with parallel fifths?

What is Wrong with Parallel Fifths?

This lesson is for you if you can’t understand why a certain style of musical harmony forbids the use of parallel fifths and octaves. The question often is something like “Why can’t we just write whatever sounds good?” Every student goes through some frustration with this issue so in this lesson we’re going to clear it up.

So what’s wrong with parallel fifths? The issue is that the notes of a perfect fifth blend so well together that they almost sound like one note rather than two. This makes parallel fifths out of style IF that style demands independence of voices.

Don’t worry if this is not entirely clear yet. In this lesson we’re going to explore the issue in depth. We’ll see what parallel fifths really are, learn when (and why) they are acceptable and how to avoid them altogether if need be. 

What are Parallel Fifths? 

Parallel fifths (also known as consecutive perfect fifths) occur when an interval of the perfect fifth moves to another perfect fifth. Here, for example, the perfect fifth C – G moves up to another perfect fifth: E – B. (Notice that when we speak about intervals, we always begin from the lower note). 

An example of parallel fifths: C - G to E - B
An example of parallel fifths: C – G to E – B

And here, the perfect fifth G – D moves down a step to another perfect fifth: F – C and then another step further to another perfect fifth: E – B. These are parallel fifths: 

An example of parallel fifths: G – D to F – C to E – B

Where it gets a little tricker is when we write for 4 parts (or 4 ‘voices’) as we do when we study harmony and voice leading. In this type of music and theory exercises, parallel fifths can be hidden inside several notes. 

Look at the example below written for 4 voices: Soprano (S), Alto (A), Tenor (T) and Bass (B). The progression is tonic to subdominant in the key of C major: that’s the progression from the chord of C major to the chord of F major arranged for 4 parts: 

An example of parallel fifths in the outer voices of 4-part harmony: C - G to F - C.
An example of parallel fifths in the outer voices of 4-part harmony: C – G to F – C

In the first chord above, the interval between the bass (playing the note C) and the soprano (playing the note G) is of a perfect fifth. In the second chord, the interval between the bass (playing the note F) and the soprano (playing the note C) is also of a perfect fifth. 

In other words, the soprano and the bass move in parallel perfect fifths, also known as consecutive fifths. Here is another example with the same progression. The consecutive fifths this time are between the bass and tenor voices. 

An example of parallel fifths between bass and tenor in 4-part harmony.
An example of parallel fifths between bass and tenor in 4-part harmony

So as the examples show, parallel fifths (or consecutive fifths) occur when any two voices move together in perfect fifths. The same goes for parallel octaves. They occur when any two voices move together in perfect octaves.

Why are Parallel Fifths Bad? 

The intervals of the perfect fifth and the perfect octave produce what’s known as open consonances (or perfect consonances). This means that these notes go so well together they almost melt into one sound.

While there are fascinating psychoacoustic reasons for this, we don’t really need to get into the science here. Instead, let’s compare some intervals and listen to this for ourselves. 

Compare the sound of a perfect fifth to, for example, a major 2nd and you’ll see what I mean. The notes that make up the perfect fifth blend effortlessly into one sound, while the interval of the major 2nd don’t:

Comparing the sound of a perfect 5th to that of a major 2nd

Comparing the sound of a perfect fifth to that of a major second

And in the same way, let’s compare a perfect octave (also an open consonance) with the interval of a minor 7th. The minor 7th is a dissonant interval, which means that it carries some level of tension. The perfect octave is so consonant that the 2 notes pretty much blend into one sound and it produces no tension whatsoever. 

Comparing the sound of a perfect octave to that of a minor seventh.

Now this doesn’t mean that consonant intervals are better than dissonant ones or that we should avoid dissonance because it means tension. Music works well with ups and downs and contrasts so we really need both!

What it does mean is that because of their open consonance quality, parallel perfect fifths and octaves don’t sound like separate, individual voices. This spoils the independence of the musical parts that we’re aiming for in the study of 4-part writing and voice leading. 

In this style, known as the Common Practice Period, parallel fifths and octaves tend to leave a blank space, or a gap, in the musical texture (the overall sound) as if a voice has disappeared. This is why, in this context, parallel fifths are bad. 

Let’s compare these two extracts for an even better illustration. The first one is from a chorale by Bach: 

Bach: Gottes Sohn ist kommen

These 4 bars by Bach clearly consist of four distinct voices. Here Bach avoids parallel fifths and parallel octaves to establish 4 independent parts. This is typical of the style: the parts are independent melodically but held together by the same chord progression.

Now listen to this extract from a piano piece by Edvard Grieg: 

Grieg: “Bell Ringing”, from Lyric Pieces Book 5, Op. 54

This piece is composed of two sets (two layers) of parallel perfect fifths: one high (played by the pianist’s right hand) and the other low (played by the left hand). Each set is clearly meant to be heard as one sound that, as the title of the piece suggests, imitates the ringing of bells. So even though the piece is composed of 4 notes at a time, it’s not a four-part composition but a two-part: one high and one low with each part consisting of 2 notes at a time. That is the power of parallel fifths!

So composers of the 18th and 19th centuries avoided parallel fifths and octaves whenever their intention was to create independent voices (or melodies) sounded together. 

When are Parallel Fifths Allowed?

Parallel fifths are OK when independence of voices is not the intention or not important for the style of the piece. Composers use parallel fifths in various ways for a variety effects, such as to embellish a main melody or to strengthen a bass line.

The example that we just heard from Grieg’s piece Bell Ringing is a great one. The two sets of parallel fifths create two parts in the music even though there are 4 notes at a time. 

The same happens in a lot of pop, rock and metal music when the guitar plays what’s known as power chords. Power chords are 3-note chords consisting of a perfect fifth plus a perfect octave:

C5 = C power chord

Often, that top note is left out from the power chord making it just another perfect 5th interval.

Here’s a typical example of power chords in use. Even though there are 2 notes at a time at all times, the intention is not to create 2 independent melodies. The intention is to have one melody intensified:

Black Sabbath: Iron Man Riff

Without that added 5th, the riff sounds ’empty’ and doesn’t make as much of an impact.  Here’s what it would sound like:

Black Sabbath: Iron Man Riff (without power chords)

A similar thing happened in the music of around 1000 years before. One of the earliest experiments in embellishing a main melody (that we know of) was by doubling it a fifth below. The purpose of the parallel fifths in the example below is not to produce separate melodic lines but to elaborate the main chant. 

Parallel fifths in a Chant from the 9th century

And the same happens yet again with consecutive perfect octaves. In this next example, which is typical of piano music, the melody is played in octaves. Clearly these aren’t wrong and they aren’t mistakes either. They are simply meant to strengthen the line. This sort of thing also happens often in orchestral music where two or more instruments play the same melody in different octaves. It still counts as one melody.. 

Beethoven: Piano Sonata no. 6, Op. 10 - 2nd movement

Beethoven: Piano Sonata no. 6, Op. 10 – 2nd movement

How to Check for Parallel Fifths

Before you continue any studies in harmony and counterpoint, you should be able to identify all intervals quickly. Intervals are the basis of chords and melodies and they’re vital for 4-part harmony. They’re also essential to recognise and avoid parallel fifths and octaves. 

To check for parallel fifths in your writing, go through this simple 3-step process: 

  1. Identify chords one at a time starting from the bass,
  2. Determine which voices (if any) are producing a perfect fifth within that chord,
  3. Check which interval the perfect fifth moves to. If it’s any interval other than a perfect fifth, you don’t have parallel fifths here. 

With a little practice, you’ll be able to perform this 3-step process instantly and mentally. 

How to Check for Parallel Fifths in Sibelius (Notation Software)

If you notate music in Sibelius, there’s a nifty trick (i.e. a plugin) to check for parallel fifths and octaves. In recent Sibelius versions, the plugin is built-in. To use it:

  1. Highlight the parts of the music you want to check (or CTRL + A to highlight it all); 
  2. Go to Review, then plugins and select “Check for Parallel 5ths/8ves”
  3. Give it a few seconds to run and if it finds any, it will tell you how many parallel fifths and octaves you have and where they are. 
  4. If you don’t have any, it will simply say that no parallel fifths and octaves were found. 

How to Check for Parallel Fifths in MuseScore

If you use MuseScore to notate music, there’s a similar plugin that checks for parallel fifths and octaves. At the time of writing, it’s available here.

4 Tips on How to Avoid Parallel Fifths

Here are four tips to avoid writing parallel fifths and octaves in your 4-part harmony exercises.

  1. Vary the arrangements (the spacing) of your chords. Sometimes the 5th of a chord is on top, other times it’s in the middle. Sometimes the root is in the bass (so the chord is in root position) and other times it’s the 3rd that goes in the bass (so the chord is in first inversion).

    You will find that in doing so, the perfect fifth that is a part of every chord goes to different voices and sometimes, it is inverted into a fourth. This variety will help you avoid parallel fifths and it will keep your music interesting too. 

  2. Follow the voice leading guidelines that you’ve studied so far. You don’t have to know all the rules all at once but all of them are there to help you create good 4-part harmony. Make sure you follow them no matter which level you’re at in the moment. 

  3. Pay particular attention to chord progressions whose roots are just a step away from each other. Common examples are the subdominant (IV) moving to the dominant (V) and the tonic (I) moving to the supertonic (ii). 

  4. An interval of the 12th moving to a 5th, or the interval of a 5th moving to a 12th still count as parallel fifths. 

Unequal Fifths: Parallel Fifths to Diminished Fifths

Unequal fifths are a pair of fifths where one is perfect and the other isn’t (most usually a diminished fifth). Since the sound of the diminished fifth is very different from that of the perfect fifth, unequal fifths do not hinder the independence of our parts so they don’t require the same treatment. 

Here is an example of unequal fifths. The top voices (soprano and alto) move from a perfect fifth to a diminished fifth. This is perfectly acceptable in 4-part writing. 

Unequal fifths: Perfect fifth followed by diminished 5th

Unequal fifths: Perfect fifth followed by diminished 5th

Here is another example. In this one, the perfect fifth sung by the bass and tenor voices becomes a diminished fifth in the next chord. This is also perfectly fine in 4-part writing. 

Unequal fifths: Perfect fifth becomes a diminished fifth

Unequal fifths: Perfect fifth becomes a diminished fifth

Common Questions about Parallel Fifths

Is it a parallel fifth if I repeat the same fifth? No, parallel fifth occur only with different perfect fifths. The same perfect fifth (or perfect octave) repeated is not considered a parallel because no change in harmony occurs.

Here’s another piano piece by Grieg in which the left hand repeatedly plays a perfect fifth (notes D and A). These repetitions don’t have the same effect as consecutive fifths as they simply repeat the same sound – the same harmony. 

Is a perfect fifth followed by a perfect octave allowed? Yes. Parallel fifths occur only when a perfect fifth is followed by a different perfect fifth. A perfect fifth followed by a perfect octave, or vice-versa, is a change of sound so it doesn’t have the same effect of parallels. 

Are parallel fifths valid only for vocal music? No even though we use the word ‘voice’ we’re not necessarily referring to sung lines only. In harmony, the word ‘voice’ can mean a human voice but it can also mean a ‘melody’, a ‘part’ or a ‘line’ (implying a ‘melodic line’). 

Whether the music is sung or played on instruments, parallel fifths and octaves are avoided IF the melodies are meant to be independent. 

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