Making Sense of Intervals in Music
1. What is an Interval? 🤔
In music the word “interval” is used to simply describe the distance between two notes. We label how notes relate to each other for many reasons, however, the most important reason is that it helps us make sense of how combinations of notes might feel when played together.
There are two steps that we take in order to label note relationships. Firstly, we label a note relationship by the number of notes that separate them alphabetically.
If “C” is note “1”, then “D” is note “2” and a the relationship between C and D would be described as a “2nd”.
If we have two notes that are exactly the same pitch (played on two different instruments for example, a C to the same C) then we would describe this interval as “unison”.
If we have two notes that are 8 notes apart (a C to the next C) then this interval is described as an “octave”.
We can also describe notes that are beyond an octave and we can do this in 2 ways. Firstly we can continue describing them as a 9th, 10th, 11th etc… Alternatively we can describe these intervals by using the word “compound” and starting back at a “2nd” again!
So, C to the next C is described as an octave and a C to D above that octave can be described as a “compound 2nd” as well as a “9th”.
The second step we need to take when describing intervals helps us describe the quality of sound that we hear. In a regular scale each of the intervals is described as having either a “major” or “perfect” relationship with note 1 in the scale. The strongest note relationships and the “pillar” notes in a scale are the notes 1, 4 and 5, so these intervals are described as “perfect” when played with note 1, whereas notes 2, 3, 6 and 7 are described as “major” because these have a more distinct tonality and quality of sound when played with note 1.
This means that in a C major scale (C D E F G A B), we would describe the intervals like this:
This is how we describe the relationships between notes in a scale!
2. Regular Scale Intervals 🎹
When working out any interval or describing any note relationships we always work out the interval from the scale of the lowest of the two notes. If the lower note is an A and the upper note is a D then we use an A major scale to work out the interval. In this case that would be a perfect 4th (A major scale - A B C# D E F# G#).
Let’s take the example of a D major scale, the notes in a D major scale are D E F# G A B and C#. Some of the notes in this scale are sharp (“#”) notes, however because these sharps are what we are expecting within a D major scale these notes are described as “perfect” or “major” in relation to a D (note 1).
This means that no matter which scale a piece of music is using, if you are working out the interval between two notes you always work it out using the scale of the lowest of the two notes rather than then scale of the piece of music. This is because we are simply working out how the two notes relate to each other, rather than how they relate to the piece of music!
If a piece of music is using an A major scale but the two notes we are labelling are D-F# then we will use a D major scale to work out the interval, because this is the lowest of the two notes.
3. Up and Down ⬆️⬇️
This takes care of notes that are within the scale…but what happens if the upper note doesn’t belong to the scale of the lower note? Well we can also describe these note relationships by describing the intervals as “minor” “diminished” or “augmented”.
If we move an interval up a half step from the note we expect within the scale, then this becomes an “augmented” interval. Using the scale of C major, if we have a perfect 4th (C-F), this would become an augmented 4th if we saw a C-F#. This is because an F# is 1 half step above the type of F that we expect to see in a C major scale.
If we had a major 3rd using a D major scale (D E F# G A B C#) we would have the notes D-F#. To make this interval an augmented 3rd we would raise the F# to an Fx (F double sharp - played as a G on the piano). So a D-Fx is an augmented 3rd!
If we lower an interval by a half step, then we label this either “minor” or “diminished”. If the scale note would normally be a “major” interval and we lower it a half step then this is becomes a “minor” interval. If the scale note would normally be referred to as a “perfect” interval, then if we lower it a half step then this is called a “diminished” interval.
So if we have the notes C-Eb, we would normally expect to see a C-E using a C major scale (C D E F G A B) and a C-E is a major 3rd. To get a C-Eb this has been lowered by a half step and so we would call a C-Eb a minor 3rd. However, If we have the notes C-Gb, a C-G would normally be called a perfect 5th and so if we lower this a half step to C-Gb then this would become a diminished 5th.
If we have the notes D-F, normally in a D major scale (D E F# G A B C#) the type of F we would expect to see is an F#. So a D-F# is a major 3rd, this means the F has been lowered by a half step and so a D-F is a minor 3rd.
If the interval we expect to see is a major interval, then we can lower it 1 half step to become “minor” but we can also lower a major interval TWO half steps, this would then also becomes a diminished interval. So C-Ebb (E double flat - played as a D on the piano) would be a diminished 3rd, because a C-E is a major 3rd, a C-Eb is a minor 3rd and a C-Ebb is a diminished 3rd.
4. Why Learn Intervals? 🙋🏻♂️
While it can initially appear quite confusing as to what different intervals are called, the more familiar with scales you become, the more clear it becomes as to whether the notes are what we expect in that scale or not. The idea is that if you can play a “minor 6th” (for example) then no matter what note you start on, you will understand how that interval will sound and feel based on the relationship between the two notes.
Many of the chords we have in music are named and understood by the intervals that are within the chord:
A major chord contains a major 3rd (e.g. C E G).
A minor chord contains a minor 3rd (e.g. C Eb G).
A diminished chord contains a diminished 5th (e.g. C Eb Gb).
An augmented chord contains an augmented 5th (e.g. C E G#).
A major 7th chord contains a major 3rd and a major 7th (e.g. C E G B).
A minor 7th chord contains a minor 3rd and a minor 7th (e.g. C Eb G Bb).
A diminished 7th chord contains a diminished 5th and a diminished 7th (e.g. C Eb Gb Bbb).
Understanding these note relationships and becoming familiar with how they sound can help you hear different chord qualities and develop your ability to play by ear, read and understand sheet music and write music with a particular sound in mind. So, try them out and see if you can hear the different qualities that intervals can make!
Matthew Cawood
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