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Context
There are times when intervals of the same number of semitones require alternate interval names.
When taken out of context, this difference can’t be heard, and in fact, without the right context there’s no reason to use an unusual interval name. However, the same size interval can sound unrecognisably different in different contexts and requires different note names and interval names to reflect this.
Even if you don’t use note names in your practice, it’s worth becoming acquainted with augmented and diminished intervals. You can definitely feel the difference in the appropriate context.
Augmented And Diminished
In 16. Intervals 1: Major, Minor And Perfect Intervals there was one interval which was unnamed; the interval of 6 semitones. There isn’t a note 6 semitones above the root note in either the major or minor scale so we can’t call it a major, minor or perfect interval. Instead, we describe it as being 1 semitone larger than a perfect 4th or 1 semitone smaller than a perfect 5th.
Just as a note can be sharpened or flattened, an interval can be augmented or diminished.
- Augmented means that the interval is 1 semitone larger than the corresponding interval in the major scale (major or perfect).
- Diminished means that the interval is 1 semitone smaller than the corresponding interval in the minor scale (minor or perfect).
Let’s look at the interval ruler on A:
The note 6 semitones above A could either be called D# or Eb.
- If the interval is A-D# we call it an augmented 4th; a perfect 4th plus 1 semitone.
- If the interval is A-Eb we call it a diminished 5th; a perfect 5th minus 1 semitone.
The same applies for other intervals with unusual note names. Most notes have two or more possible names, resulting in different interval names.
For example:
- A to C# is a major 3rd
- A to C double sharp is an augmented 3rd, 1 semitone larger than A to C#
- D is a perfect 4th above A
- Db is a diminished 4th above A, 1 semitone smaller than D to A
NOTE: Remember to always count intervals from the lower note to the upper note. Use the major and minor scales of the lower note to find the upper note and name the interval.
Example:
Interval names are based on note names as well as size, so even though A-C# and A-Db are the same number of semitones apart, they can’t have the same interval name.
A-C#
- C# is the 3rd note of A major, so
- A-C# is a major 3rd
A-Db
- There is no Db in A major or A minor. There is a D natural, though, the 4th note of both A major and A minor.
- A-D is a perfect 4th.
- Db is 1 semitone lower than D, so A-Db is 1 semitone smaller than A-D.
- A-Db is a diminished 4th.
In general, if the upper note of an interval doesn’t fit either scale of the lower note, look for the nearest note in the scale with the same letter.
- If the upper note is 1 semitone higher than the equivalent note in the major scale, the interval is augmented.
- If the upper note is 1 semitone lower than the equivalent note in the minor scale, the interval is diminished.
NOTE: Augmented and diminished intervals can involve the occasional double-sharp or double-flat, depending on the lower note.
If the lower note is a sharp, an augmented interval will most likely require the upper note to be a double sharp. Similarly, if the lower note is a flat, a diminished interval would probably require the upper note to be a double flat.
Don’t be concerned. Just stick to the method:
- sharpen = 1 semitone higher without changing the note name
- flatten = 1 semitone lower without changing the note name
Interval Names Summary
- 2nds, 3rds, 6ths and 7ths have four possible qualities. From largest to smallest they are augmented, major, minor, diminished.
- 4ths, 5ths and 8ths have three possible qualities. From largest to smallest they are augmented, perfect, diminished.
- It’s possible to have an augmented 1st but a diminished 1st is meaningless. There’s no such thing as a negative interval. Intervals are absolute…
- 8ths can be diminished or augmented but they should be called eighths, not diminished or augmented octaves. By definition, an octave is a perfect 8th.
Here’s a list of all intervals within an octave, with examples on C showing all the interval names including augmented and diminished intervals for each degree.
Here’s the same list of intervals shown as an interval ruler on C.
Just a reminder: the scales used to count intervals are built on the lower note of an interval and serve as a ruler to measure the name of the interval, in this case an interval whose lower note is C. For an interval with a different lower note we use scales on the new note to measure the interval.
The interval ruler is no indication of the actual key of the piece! The actual key is determined by the key signature and the overall root note.
Why have two names for the same size interval?
Good question! Interval names are based on note names. Note names reflect a specific musical context. The same size interval can sound unrecognisably different in different contexts.
An interval name describes both the size of an interval and how many letters there are from the lower note to the upper note. This allows us to “reverse engineer” an interval name and arrive at the right note names as well as the right sound.
In the next lesson we will see a practical example of the use of an alternate interval name.
Why are there two note names for most notes?
There are actually more than two if you count double sharps and double flats…
The choice of note name depends on the context.
- If a note belongs to the key of the piece, its name is determined by the key signature.
- If a note doesn’t belong to the key, its name is based on which note in the key it replaces.
When reading a new piece, the reason for some note names may not be apparent. In the coming lessons we will encounter some examples where an unusual note name is required. You can see and hear two of these in Sleight Of Ear.
In the meantime, let’s assume that unusual note names are used for a reason, so interval names need to be able to reflect which note name is used.
How To Name An Interval
- Write out the interval ruler; the major and *minor (phrygian) scales built on the lower note of the interval. One way to do this is to write out the major scale then flatten the 2nd, 3rd, 6th and 7th notes to get the *minor.
- Look for the upper note of the interval in these scales.
- If the upper note is in either scale or in or both scales, name it as we’ve already learnt, as a major, minor or perfect interval. You have the answer.
- If it’s not in either scale, find the note of the same letter that’s closest in pitch to the upper note of the interval.
- If the upper note is 1 semitone higher than the note of the same letter in the major scale, the interval is augmented.
- If the upper note is 1 semitone lower than the note of the same letter in the *minor scale, the interval is diminished.
- The degree is always the number of letters from the lower to the upper note, inclusive.
Try These…
Below is a blank interval ruler you can use as a template. For each of the following exercises, first write the scales of the lower note as per the template.
A. Name the following intervals, keeping the above method in mind:
- A-G
- A-Gb
- C-C#
- C-E
- C-E#
- Bb-Ab
- Bb-Abb
- D-A
- D-Ab
- D-G#
How To Name The Upper Note Of An Interval
- Write out the interval ruler; the major and *minor (phrygian) scales built on the lower note of the interval.
- For major, minor or perfect intervals, find the upper note by following where the degree and quality of the interval name intersect.
- If the interval is augmented, sharpen the same letter note in the major scale.
- If the interval is diminished, flatten the same letter note in the minor scale.
Try These…
B. Name the upper note of the following intervals. For the degree, count letters (including the starting note).
- If the interval is augmented, sharpen the equivalent note in the major scale.
- If the interval is diminished, flatten the equivalent note in the minor scale.
- major 6th above G
- augmented 6th above G
- major 7th above G
- augmented 7th above G
- minor 3rd above E
- diminished 3rd above E
- perfect 5th above E
- diminished 5th above E
- minor 6th above C
- diminished 6th above C
Answers at the end of this post.
Shortcuts
It may seem laborious to have to write out scales every time you want to name an interval.
If you know your keys well, you can do this in your head. In part, I have encouraged the learning of at least the key signatures of the major keys for this very reason. As we’ve seen, you can find the *minor by flattening the 2nd, 3rd, 6th and 7th notes. Key relationships also provide some shortcuts for remembering keys. Have a quick look at the relevant lessons from Part 1 if you’re not sure…
The good news is that there are a number of shortcuts to help us to name intervals without writing out scales. These will become apparent over the next few lessons.
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NEXT LESSON: B3. Melodic And Harmonic Minor
PART 2 CONTENTS: Basic Music Theory Course Contents
Answers to Try These…
A.
- minor 7th
- diminished 7th
- augmented 1st
- major 3rd
- augmented 3rd
- minor 7th
- diminished 7th
- perfect 5th
- diminished 5th
- augmented 4th
B.
- major 6th above G = E
- augmented 6th above G = E#
- major 7th above G = F#
- augmented 7th above G = F##
- minor 3rd above E = G
- diminished 3rd above E = Gb
- perfect 5th above E = E
- diminished 5th above E = Eb
- minor 6th above C = Ab
- diminished 6th above C = Abb