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Diminished and augmented intervals

Now we want to try to classify the tritone with its special position in our interval system. To do this we must address the interval naming a little closer, because really, what is a tritone starting from C? An F sharp or a G sharp? If we want to write down the notes, we need to differentiate.

To do this I will introduce the terms diminished interval and augmented interval. Every interval, regardless of whether it is pure, minor or major, can be diminished by reducing it by a half tone, or augmented by increasing it by a half tone.

With pure intervals using the pure C - F fourth as an example this is as follows:

C - F flat = diminished fourth

C - F = pure fourth

C - F sharp = augmented fourth

Here is an example for major and minor intervals:

C - E double flat = diminished third

C - E flat = minor third

C - E = major third

C - E sharp = augmented third

A minor interval can only become a diminished interval. It cannot be augmented, because if we increase the minor interval by a half tone, it becomes a major interval. First of all the major interval becomes the augmented interval by increasing by a half tone. The major interval, however, cannot be diminished because of this.

Of course most diminished or augmented intervals can be enharmonically changed, and therefore are much easier to write down. C - E double flat can be written as C - D, only then it is a major second, and not a diminished third.

"What’s all this for?”, you may ask, tearing at you hair! Well, sometimes it is simply more logical to name intervals like this; more on this with the chords, when we get to the “stacked thirds” topic. Generally speaking you will hardly ever use it, apart from one exception – the tritone. This is usually given as a diminished fourth, which strictly speaking is not quite right, as it is actually to be considered an augmented fourth. But I don’t want to be so precise about this just now.

Overview of all intervals within the octave, using C major as an example
Interval Name Comment
C - C flat Diminished prime (sounding like a minor second downwards)
C - C Pure prime  
C - C sharp Augmented prime (sounding like a minor second)
C - D double flat Diminished second (sounding like a pure prime)
C - D flat Minor second  
C - D Major second  
C - D sharp Augmented second (sounding like a minor third)
C - E double flat Augmented third (sounding like a major second)
C - E flat Minor third  
C - E Major third  
C - E sharp Augmented third (sounding like a pure fourth)
C - F flat Diminished fourth (sounding like a major third)
C - F Pure fourth  
C - F sharp Augmented fourth (tritone)
C - G flat Diminished fifth (tritone)
C - G Pure fifth  
C - G sharp Augmented fifth (sounding like a minor sixth)
C - A double flat Diminished sixth (sounding like a pure fifth)
C - A flat Minor sixth  
C - A Major sixth  
C - A sharp Augmented sixth (sounding like a minor seventh)
C - B double flat Diminished seventh (sounding like a major sixth)
C - B flat Minor seventh  
C - B Major seventh  
C - B sharp Augmented seventh (sounding like a pure octave)
C - C flat Diminished octave (sounding like a major seventh)
C - C Pure octave  
C - C sharp Augmented octave (sounding like a minor ninth)

Here’s another small tip on determining diminished and augmented intervals. The note name to determine the interval distance is critical. Let’s determine the C - C sharp interval.Both notes have the base name, C, therefore it is a prime. A prime is a pure interval, but as, in contrast to C, C sharp is increased by a half tone, the pure interval becomes an augmented interval. C - C sharp is an augmented prime.

Now let’s look at the C - D double flat interval. This sounds like a prime, but the base notes C - D have the distance of a second, or more precisely, of a major second. C - D flat is then the minor second; C - D double flat is therefore then a diminished second.

 Hmmm. Rather confusing! Don’t worry about it – it was exactly the same for me with the writing. I looked at it like this: I can’t hear all this anyway, so it’s not so bad if I haven’t understood everything. This is also pretty rough theory, so it’s more important first of all to understand the “normal” intervals.

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