Interval Identification | Diminished And Augmented Intervals (9 of 10)
A diminished interval occurs when a minor or Perfect interval is flattened by one half step.
Diminished Intervals from Minor
For example, in video seven of this series we learned that, because the two notes are separated by ten consecutive half steps, an interval of a minor seventh above the note A is the note G.
Knowing that a diminished interval is created when a minor interval is flattened by a half step, if an interval of a minor seventh above A is G, then an interval of a diminished seventh above A would be the note G-flat.
Now, the note G-flat is the enharmonic equivalent of the note F-sharp, meaning both letter names are in fact the same pitch.
Therefore, you may have noticed that an interval of a diminished seventh above the note A sounds exactly the same as an interval of a Major sixth.
However, because we are currently discussing an interval of a diminished seventh, we must use the letter name G-flat rather than F-sharp. That is because an interval of a diminished seventh is an alteration of a minor seventh interval which is in fact the note G.
Diminished Intervals from Perfect
As stated earlier, another way that a diminished interval is created is when a Perfect interval is flattened by one half step.
For example, in video five we learned that an interval of a Perfect fifth above the note C is the note G.
To play an interval of a diminished fifth above the note C, simply flatten the note G by one half step. Here you can see that an interval of a diminished fifth above the note C is the note G-flat.
Augmented Intervals from Major
On the other hand, an augmented interval occurs when the top note of a Major or Perfect interval is raised by one half step.
In video six we learned that, because they are separated by the distance of nine consecutive half steps, an interval of a Major sixth above the note G is the note E.
If we raise the note E by one half step we will have created an interval of an augmented sixth.
Now again, even though E-sharp and F are enharmonic equivalents, or different names for the same pitch, because an augmented sixth is an alteration of an interval of a Major sixth, we must use the letter name E-sharp.
Augmented Intervals from Perfect
Seeing how Perfect intervals can be augmented as well, if an interval of a Perfect fourth above the note C is the note F,
then an interval of an augmented fourth above C is therefore the note F-sharp.
Tritones
A tritone is a unique interval in that, because the distance separating each note is six consecutive half steps, it is exactly half the amount of steps as a Perfect eighth, or octave.
For example, six consecutive half steps above the note B is the note F.
Now, seeing how an interval of a Perfect fifth above B is the note F-sharp, and F natural is one half step lower than F-sharp, this interval of B natural to F natural is therefore considered to be an interval of a diniminished fifth
Another six half steps above the note F brings us back to the note B.
B natural, being one half step above the note B-flat, is an interval of an augmented fourth above F.
In other words, a tritone can either be a diminished fifth, or an augmented fourth, depending upon which way you look at it.
Because of its dissonant sound quality, tritones create vibrational tension within the Dominant seven chord so that resolution to the tonic may be more apparent.
For example, the notes of a G Dominant seven chord are G, B, D, and F. As we have just discovered, the interval between the note B and the note F is a tritone. Resolving these notes to the tonic chord C Major gives the listener a greater sense of completion.
