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Victoria Williams

LmusTCL BA Mus (Hons) MISM

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Next UK ABRSM Online Theory Exams Grades 1-5:
16th March 2021
Next UK Trinity Paper-based Theory Exams Grades 1-8:
Sat 8th May 2021

Grade Three Music Theory - Lesson 9: Intervals

Suitable for:  ABRSM Grade 3   Trinity Grade 3   GCSE   AP Music Theory Beginners 

Interval Number

We can describe an interval by using a number. For example, this interval is a 5th, because there are five letter names between the lowest and the highest:

G-A-B-C-D = 5 letter names

At this grade, the lowest note is always the tonic (keynote), or first degree of the scale. (In later grades you’ll find that the lower note can be anything at all!) To find the number of the interval, all you need to do is work out the degree of the scale.

D is the 5th degree of the scale of G major.


In the grade three music theory exam, you need to describe an interval with its number and also its type. You also need to know all the intervals in the new key signatures for this grade too, of course!


Interval Qualities

We will learn about three types of interval for grade three:

  • Major intervals
  • Minor intervals
  • Perfect intervals


Major Keys

In a major key, all the intervals are either major or perfect. There are NO minor intervals in a major key (when the lowest note is the tonic).

Here is the scale of C major, showing each interval type when the lowest note is the tonic:
intervals in a major key

In all major scales, the unison, fourth, fifth and octave are PERFECT intervals. All the other intervals are MAJOR


Here are some examples of intervals from other major keys:
intervals examples


Minor Keys

In minor keys you will find major, perfect and also minor intervals. Minor intervals are always one semitone smaller than the major interval with the same number.

Intervals are based on the harmonic minor scale, or the melodic minor scale. Don't forget that this means the 6th and 7th degrees of the scale are sometimes raised by a semitone (half step)!

  • Perfect intervals are the same in both major and minor keys: all unisons, 4ths, 5ths and octaves are perfect, whether the key is major or minor.
  • The interval of a 2nd is major in both major and minor keys.
  • In a minor key, the interval of 3rd is minor, whereas in a major key it is major.
  • The intervals of a 6th and 7th are major in major keys, but can be major or minor in minor keys.

Here are the intervals built from the tonic of the G major and G minor scales.
intervals grade 3 music theory

The same pattern of major/minor/perfect intervals can be made from any tonic starting note.

You can see that only three intervals are different, between the major and minor versions of the scale - the 3rd, 6th and 7th.


Intervals at a Glance:

 Number from Tonic
Major Scale Type Minor Harmonic Type Minor Melodic Type 
 Unison  Perfect Perfect Perfect
 2nd  Major Major Major
 3rd  Major Minor Minor
 4th  Perfect Perfect Perfect
 5th  Perfect Perfect Perfect
 6th Major Minor Major or minor
 7th Major Major Major or minor
Octave Perfect Perfect Perfect

Describing Intervals

You will probably get a question asking you to describe some intervals by giving the type and number, like this:

describe this interval giving type and number
Type ………………
Number …………… 

  • Notice that they key is given to you – this interval is in G minor.
  • The lowest note will always be the tonic.

Starting at the lower note, count how many letter names of notes there are up to the higher one.

G-A-Bb = three notes.

This interval is a third. The key is minor, so it will be minor third (remember that 3rds and 6ths above the tonic are minor intervals in minor keys).


Type: minor
Number: third


 Intervals can be written vertically ("harmonic") or horizontally ("melodic").



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