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Grade Five Music Theory Lesson 7: Intervals

 

You might also like to watch our video lesson on intervals:

 

 

Intervals

An “interval” is the distance between any two notes. Each interval has a number and a quality, which you have to know for Grade 5 Music Theory.

“Melodic intervals” are read horizontally and are found in melodies, whereas “harmonic intervalsare read vertically, and are found in chords.

They are described in the same way.

B-D as a melodic (horizontal) interval:

Melodic intervals

B-D as a harmonic (vertical) interval:

Harmonic interval

 

 Interval Numbers

To find the number of an interval, first find the note names of the two notes, (ignore any sharps and flats for now), and count the letter names, starting with the lower note on the stave.

Some examples: 

Letter Names
(start with

lower note)

No. of

Notes

Interval

Number

Example

F-G

2

a second

A second

B-D

3

a third

A third

B-D sharp

3

a third

a third

E-A

4

a fourth

a fourth

C sharp - G sharp

5

a fifth

a fifth

C-G sharp

5

a fifth

a fifth

D-B flat

6

a sixth

a sixth

A-G

7

a seventh

a seventh

 

If the letter name is the same, the interval will be either "unison" (the same note), or "octave" (the next one up or down).

A unison

G-G is a unison

 

An octave

G-G1 is an octave

 

 Starting on the Higher Note - a Very Common Mistake!

What happens if you try to calculate an interval by starting with the higher note on the stave? You will get the wrong answer! This is a common mistake, so let’s look at an example of what can go wrong. What is the following melodic interval?

What is this harmonic interval 

Smiley faceFirst, the correct way: starting on the lower note (C), we count letter names to the higher note, (G), C-D-E-F-G =5, which gives us a 5th. This is the right answer! 

Sad faceNow the wrong way. Starting on the first note (G), we count the letter names to the second note (C), G-A-B-C =4, which gives us a 4th. This is the wrong answer!

 

Interval Qualities

Each interval has quality name which goes before it, for example “major sixth”.

There are 5 quality names which are: perfect, major, minor, augmented and diminished.

We will look at each of these interval qualities in more detail. 

 

Major and Perfect Intervals

If you take a major scale, all the intervals which are built from the tonic of that scale are either major or perfect. You can think of "major and perfect" as the kind of "default intervals". Here's an example. Look at the scale of G major, where G is the tonic (keynote).

tonic-of-major-scale

If the lower note of an interval is G, and the upper note is one which exists in the G major scale, its quality will be either major or perfect.

Major intervals are the 2nd, 3rd, 6th and 7th, and perfect intervals are the unison, 4th, 5th and octave. (Notice that there are four of each kind).

major-scale-intervals

The same is true of any major scale. So, in order to understand intervals, it is essential that you are confident in your scales!

If the upper note in an interval is not part of the major scale built from the lower note, then the interval cannot be major or perfect. Instead, it will be augmented, minor or diminished.

Augmented Intervals

When an interval is wider by one semitone (half step) than the one found in the major scale, then the interval is augmented

Here's an example:

augmented-5th

First, work out the interval number: count up the letter names (ignore any accidentals). G-A-B-C-D = 5 notes = a 5th.

Next look at the 5th in the G major scale: the note is D natural.

In this interval, we have D sharp instead. The D# means that this interval is one semitone wider than the one found in the major scale.

Therefore, this interval is an augmented 5th.

In fact, if you raise each note of the major scale by a semitone (without changing the letter names of the notes*), you will make all the intervals augmented:

augmented-scale

* I.e. change G to G# and not to Ab. 

Notice that in order to raise the F# by a semitone, we need to use a double sharp.

Minor Intervals

A minor interval is one semitone (half step) smaller than a major interval.

Remember, the quality "major" applies only to the 2nd, 3rd, 6th and 7th interval numbers.

minor-6th

This interval is a 6th. In the G major scale, the 6th is E natural. E flat makes the interval smaller by one semitone, so this is a minor 6th.

(Don't fall into the trap of thinking that minor intervals occur in minor scales, and major intervals in major scales: this is only half true! While major scales don't contain any minor intervals (built from the tonic), minor scales DO contain major intervals.) 

Minor intervals only apply to 2nds, 3rds, 6ths and 7ths. You can't have a "minor 5th", for example.

Diminished Intervals

A diminished interval is one semitone (half step) smaller than a minor or perfect interval.

A diminished interval is one tone (whole step) smaller than a major interval.

diminished-4th

G to C natural is a perfect 4th. C flat makes the interval one semitone narrower, so this is a diminished 4th.

diminished-7th

G to F# is a major 7th. 

G to F natural is one semitone smaller, so it's a minor 7th.

G to F flat is two semitones smaller (than a major 7th), so it's a diminished 7th.

 

Tricky Intervals

This system for working out intervals is easy when you know your major scales. However, some major scales are more awkward than others, and some don't even really exist!

tricky-intervals

In the first case here, you'd need to know the scale of C# major (awkward, but does exist), and in the second case, you'd need the G## major scale (does not really exist!)

In cases like these, it is usually a good idea to simplify the interval. To do this, you need to

  • move both notes
  • by the same amount
  • in the same direction
  • without changing the letter name

In the first case, C# major is an awkward scale, but C major is easy. To change C# to C natural, you need to move it down by one semitoneYou need to move the upper note in the same way, down one semitone. This means A# will become A natural.

major-6th

Now work out the interval as before: the note A is part of the C major scale, so this is a major 6th. The original interval, C#-A# is also a major 6th. (And so is Cb-Ab, of course!)

Let's do the same with the second tricky interval. The lower note is G##, but G natural would make things a lot simpler. 

G## is two semitones (half steps) higher than G natural, so you need to lower G## by a tone (whole step) to get to G natural. Do the same to the upper note: move D# down by two semitones, without changing the letter name. You will arrive at Db.

diminished-5th

Now compare this interval to the one found in G major. G-D is a perfect 5th, and this is one semitone smaller, so it's a diminished 5th, and therefore, so is G##-D#. 

Compound Intervals

Intervals which are larger than one octave are called compound intervals. There are two ways to describe compound interval numbers:

  • by the actual number of notes you count
  • by using the word "compound", plus the interval an octave lower.

You can use whichever you prefer.

Compound intervals need to be qualified with the word major/minor/perfect/diminished/augmented, in the same way as non-compound intervals.

Here is a compound interval:

compound-2nd

There are 9 letter names between E and high F, so you can call this a 9th. Alternatively, you can call it a "compound 2nd", because E to F is a second plus an octave.

What is the interval's quality? Mouse over the interval to check if you were right (tap on mobile devices)!

  

Summary of Intervals:

Here’s a summary of the technical interval names, in order of size, starting with the smallest, with an example of each, up to a 7th.

Octave intervals are the same as unisons, but the upper note is an octave higher. 9ths are the same as 2nds, and so on.

One interval is missing. What do you think the interval of C to high Cb is? lightbulbette

 

complete-intervals-1

complete-intervals-2

 

 

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