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!
We will learn about three types of interval for grade three:
- Major intervals
- Minor intervals
- Perfect intervals
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:
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:
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:
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
|Major or minor
|Major or minor
You will probably get a question asking you to describe some intervals by giving the type and 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).
Intervals can be written vertically (“harmonic”) or horizontally (“melodic”).
Interval Quality Exercises
Hover your mouse over the questions (tap on mobiles) to reveal the answers.
Exercise 2 – Describing Melodic Intervals
Describe each of these melodic intervals, giving the type and number (e.g. minor 3rd, perfect 8ve). The keys are named and in case the lower note is the key note (tonic).
Exercise 3- Describing Intervals (Mixed)
Describe each of these intervals, giving the type and number (e.g. minor 3rd, perfect 8ve). Also say whether the interval is melodic or harmonic. The keys are named and in each case the lower note is the key note (tonic).
Above each of these notes, write a higher note to form the named harmonic interval. The key is given.
Exercise – Writing Melodic Intervals
After each of these notes, write a higher note to form the named melodic interval. The key is given.