Intervals & Tonal Degree Names - Part 5: Diminished Intervals
The last and final interval is the diminished interval. You can get a diminished interval by lowering a perfect or minor interval by a half step. So for the diminished intervals we will be using unisons, 2nds, 3rds, 4ths, 5ths, 6ths, 7ths, and octaves.
First the diminished unison. This is one of the weirdest one because it actually descends as you will see.
Here are all diminished unisons:
These are all a half step away, but going lower/descending. It is enharmonically the same as a minor 2nd descending.
The next interval is the diminished 2nd. This is also quite an odd interval since it is enharmonically the same as a perfect unison.
Here are all diminished 2nds:
So not only is this our first occurrence of a triple flat but it is also the only interval that doesn’t move in anyway. Now a perfect unison doesn’t move but that is because it is a unison which implies that it is the same note. A 2nd implies forward motion, ascending motion, but in this case it is enharmonically the same as the same note/ the perfect unison.
You will notice a pattern of the diminished intervals being enharmonically the same as a lot more intervals. For example the diminished 3rd. The diminished 3rd will be a half step lower than the minor third, which is already a half step lower than the major third. So in reality we are going a whole step below the major interval.
Here are all diminished 3rds:
The diminished 3rd is enharmonically the same as the major 2nd. It is a whole step away.
The diminished 4th is a half step lower than the perfect 4th and will also be enharmonically the same as a mjoar interval.
Here are all diminished 4ths:
The diminished 4th is enharmonically the same as the major 3rd. It is 2 whole steps away.
The next diminished interval, the diminished 5th is an important one, probably the most important one. Because like I said before in the augmented interval section, the augmented 4th and diminished 5th are tritones. And tritones play an important role in harmony, chords, and the diminished scales. They are a perfect diminished interval since they fold upon themselves and are the same interval when you flip them, but spelt enharmonically, not the same. For example C-Gb is a diminished 5th and if you flip it to Gb-C and or Gb-Dbb it is also a diminished 5th, but spelt differently.
Here are all diminished 5ths:
The diminished 5th is 3 whole steps away.