Tag: how to name an interval

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There are many occasions when we need to name an interval, whether to describe a quirky jump in a melody or notes in a chord. So far, naming an interval has involved finding the major scale built on the lower note of the interval. Every time we want to name an interval with a different lower note, we need a different scale!

Scales are great for learning to pitch (sing or play) intervals and they help explain how interval names work but it’s not a quick way to name intervals. Let’s see if we can streamline this rather time-consuming process…

If you’re impatient and want to go straight to the ultimate shortcut, click here. Else read on for more detail…

Counting Intervals

Interval names are a way of describing both the size (number of semitones) and degree (number of letters). To name an interval we need to count both the number of semitones and the number of letters (inclusive).

Have a look at the list of all interval names within an octave:

If you have a good memory you could simply learn the complete list of interval names and their sizes in semitones from unison to octave, by memory, just like we learn our times tables.

How To Name An Interval Using The Interval List

1. Count letters, including the starting and ending letter of the interval. The number of letters make up the degree of the interval name.
2. Count semitones.
3. Find the row with the correct number of semitones in the list and look for the correct degree to the left or right in that row.

Example: A#-F

1. A#-F is 6 letters. A#-F is a 6th
2. A#-F = 7 semitones
3. 7 semitones = perfect 5th or diminished 6th
   We already know from step 1 that A#-F is a 6th, so A#-F is a diminished 6th

Less Is More

The list of interval names is rather large, so let’s reduce it a little.

Visualise

Remember the hierarchy of interval qualities. In your mind’s eye, see their effect on the size of an interval. For a given degree, augmented is 1 semitone larger than major or perfect and diminished is 1 semitone smaller than minor or perfect.

Inversions

Remember also that the larger an interval, the smaller its inversion. Using inversions for larger intervals cuts the list in half.

The Ultimate Shortcut For Naming An Interval

Learn the major, minor and perfect intervals from 0 to 7 semitones. You can leave out 6 semitones for now, as it doesn’t have a major, minor or perfect interval quality.

I prefer to use a single letter for the quality. It makes this list look tiny… P for perfect, M for major, m for minor (I also use a for augmented and d for diminished).

For 0 to 7 semitones, that’s

P1, m2, M2, m3, M3, P4, _, P5

That’s not a very intimidating list to learn, is it?

How To Name An Interval

To name an interval, we need to know the number of letters AND the number of semitones. If it’s 7 semitones or less, we can directly find it in the list.

For example, C-Eb

• C-Eb is 3 letters so the degree is a 3rd
• C-Eb is also 3 semitones
• Check the list: the interval name for 3 semitones is a minor 3rd
• That answer matches the degree: C-Eb is a minor 3rd

If large, Invert, then Invert the Answer

If the interval is larger than 5 letters, we can invert the interval: the larger the interval, the smaller the inversion. Once we have the inversion’s interval name, we can invert the name.

For example, C-B

• C-B is 7 letters so it’s a 7th
• Invert to get B-C
• B-C is 2 letters so it’s a 2nd (7+2=9)
• B-C is 1 semitone
• The interval name on our tiny list for 1 semitone is a minor 2nd
• B-C is a minor 2nd
• Invert the interval name: minor goes with major, 2nd goes with 7th
• C-B is a major 7th

Augmented and Diminished: Bigger or Smaller than Normal

Diminished and augmented intervals aren’t in this tiny list. That’s ok because we can work out if the interval is diminished or augmented by comparing the upper note to that of the nearest interval in the list.

For example, C-F#

• C-F# is 4 letters, so it’s a 4th
• The only 4th in our mini list is a perfect 4th, 5 semitones.
• A perfect 4th above C is F
• C-F# is 1 semitone larger than C-F
• 1 semitone larger than perfect is augmented
• C-F# is an augmented 4th

How To Name Any Interval Within An Octave

This method covers all eventualities outlined above.

1. Count letters, including the starting and ending letter of the interval. The number of letters make up the degree of the interval name.
2. If more than 5 letters, invert the interval (invert the notes of the interval) and count its letters or subtract the original interval degree from 9.
3. Count semitones.
4. Find the number of semitones in the list.
5. Compare the degree in step 4 to the degree in step 1. 

• If the degree in step 4 matches the degree in step 1 we have the answer
• If the degree in step 4 is larger than the degree in step 1 the interval is augmented
• If the degree in step 4 is smaller than the degree in step 1 the interval is diminished

6. If the interval was inverted, invert the interval name.

Examples

Example 1: A-C#

1. A-C# is 3 letters, so A-C# is a 3rd
2. (If more than 5 letters, invert the interval and count its letters. N/A)
3. A-C# = 4 semitones
4. 4 semitones is a major 3rd
5. The interval is a 3rd and the list for 4 semitones is a major 3rd.
6. (If the interval was inverted, invert the interval name. N/A)

A-C# is a major 3rd

Example 2: A-B#

1. A-B# is 2 letters, so A-B# is a 2nd
2. (If more than 5 letters, invert the interval and count its letters. N/A)
3. A-B# = 3 semitones
4. 3 semitones is a minor 3rd
5. The interval is a 2nd and the list for 3 semitones is a minor 3rd. A-B# is a 2nd which is the size of a minor 3rd, 1 semitone larger than than a major 2nd.
6. (If the interval was inverted, invert the interval name. N/A)

A-B# is an augmented 2nd

Example 3: A-Cb

1. A-Cb is 3 letters so A-Cb is a 3rd
2. (If more than 5 letters, invert the interval and count its letters. N/A)
3. A-Cb = 2 semitones
4. 2 semitones is a major 2nd
5. The interval is a 3rd and the list for 2 semitones is a major 2nd.
   A-Cb is a 3rd which is the size of major 2nd, 1 semitone smaller than than a minor 3rd.
6. (If the interval was inverted, invert the interval name. N/A)

A-Cb is a diminished 3rd

Example 4: A-G

1. A-G is 7 letters. A-G is a 7th
2. Invert A-G to get G-A, which is 2 letters. G-A is a 2nd
3. G-A = 2 semitones
4. 2 semitones is a major 2nd
5. The interval is a 2nd and the list for 2 semitones is a major 2nd.
   G-A is a major 2nd
6. Major goes with minor and 2nd goes with 7th

A-G is a minor 7th

Example 5: A-Gb

1. A-Gb is 7 letters, so A-Gb is a 7th
2. Invert A-Gb to get Gb-A, which is 2 letters.
   Gb-A is a 2nd
3. Gb-A = 3 semitones
4. 3 semitones is a minor 3rd
5. The interval is a 2nd and the list for 3 semitones is a minor 3rd.
   Gb-A is a 2nd which is the size of a minor 3rd, 1 semitone larger than than a major 2nd.
   Gb-A is an augmented 2nd
6. Augmented goes with diminished and 2nd goes with 7th

A-Gb is a diminished 7th

Try These…

a) Learn the list of normal interval names from 0-7 semitones as outlined above, then name the following intervals.

F-A
C-A
F#-G
F#-D
Bb-G
B-E
C#-Ab
G#-G
Ab-B
Ab-G#

Answers at the end of this post.

Short-cut 4ths And 5ths

There’s an easy way to spot perfect 4ths and 5ths.

• A 4th or 5th is perfect if both notes have the same sign
• UNLESS the letters are B AND F (remember BCEF?)
• If the letters are B AND F, to make a perfect interval, Bb goes with F and B goes with F#

1. Count letters.
2. A 4th or 5th is perfect if both notes have the same sign, unless the letters are B AND F. To be perfect, Bb goes with F and B goes with F#.
3. If a 4th or 5th is not perfect you can work out whether it’s diminished or augmented by looking at whether it’s 1 semitone larger or smaller than a perfect 4th or 5th.

Example: Ab-E

1. Ab-E is 5 letters so Ab-E is a 5th
2. We know Ab-Eb (or A-E) is a perfect 5th because both letters have the same sign
3. Ab-E is 1 semitone larger than Ab-Eb so the interval is augmented

Ab-E is an augmented 5th

Try These…

b) Name the following 4ths and 5ths. Answers at the end of this post.

E-B
E-Bb
Ab-Db
Ab-D
F-C
F-C#
Bb-F
B-F (hint: visualise)
Db-G
G#-C#

What About Intervals Larger Than An Octave?

The easiest way to describe an interval larger than an octave is in two parts: a number of whole octaves and the remaining interval.

For example, C4 to A5 = 1 octave and a major 6th.

For more information about naming large intervals, including method of using a single interval name and a few exercises, please visit How To Name Intervals Larger Than 1 Octave.

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NEXT LESSON: B7. How To Notate Very High And Very Low Notes

PART 2 CONTENTS: Basic Music Theory Course Contents

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Answers to Try These…

Thanks to Adiela for finding two errors in my answers and letting me know

a)
major 3rd
major 6th
minor 2nd
minor 6th
augmented 6th
perfect 4th
diminished 6th
diminished 8th
augmented 2nd
augmented 7th

b)
perfect 5th
diminished 5th
perfect 4th
augmented 4th 
perfect 5th
augmented 5th
perfect 5th
diminished 5th 
augmented 4th
perfect 4th