Grade Three Music Theory - Lesson 9: Intervals

New for Grade Three Music Theory

Up to grade two, you learnt how to describe the interval between two notes using a number. For example, this interval is a 5th, because there are five notes between the lowest and the highest:

G-A-B-C-D = 5 notes

At this stage, 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 count the degree of the scale.

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

(See lesson 5 for more about Degrees of the Scale).

For grade three music theory, 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 Types

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:

In any major scale, 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:

Minor Keys

In minor keys you will find major, minor and perfect intervals. The notes that are the same as in the major version of the scale are major/perfect intervals. The intervals that are only found in the minor scale are minor intervals.

Here are the scales of G major and G minor harmonic for you to compare (don’t forget that all B and Es are flat in G minor, and that the 7th note (F) is always sharpened!)

You can see that only two intervals are different, between the major and minor versions of the scale.

These are the third and the sixth.

In a minor scale, the third above the tonic is always a minor third, and the sixth above the tonic is always a minor sixth. In the major scale, they are the major third and major sixth. All the other intervals are the same type, whether the scale is major or minor.

Intervals at a Glance:

Describing Intervals

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

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 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 are minor intervals in minor keys).

Type:              minor
Number:        third