Interval Inversions are a useful way to easily analyze musical intervals. By learning how to "turn intervals over", or invert them, you can quickly see what size and quality they have. In this basic music theory lesson you'll learn how to do this.
Inversions in music theory is when we flip things over! : )
You can invert chords, and intervals for example. When inverting intervals you simply move one of the notes an octave higher or lower.
We use interval inversions to analyze intervals. It is a "shortcut" if you like, to find the right number and quality of the interval much faster.
Look at these intervals:
So how is this useful?
It becomes extra useful when we talk about interval qualities (major, minor, perfect etc).
When the intervals are inverted, the quality becomes the opposite!
This means, that you only have to memorize two intervals' sizes:
From the Major Scale Intervals method, you learned that:
Then, you automatically know that a Minor 2nd is a half step smaller, only a semitone. And a Minor 3rd is 1 1/2 steps apart.
Let's say you quickly need to analyze this interval (the first one):
You don't even need to count to know if it's a 7th, just invert it, and since it's a 2nd- you know that the original was a 7th. How quick is that!
Here is a 6th (the first interval). How big exactly?
Now you can quickly analyze all 2nds, 3rds, 6ths and 7ths!
Well, the Perfect intervals we don't really have to practice so much since they are all perfect...
A Perfect 5th becomes a Perfect 4th and vice versa. The same with Octaves and Unisons (which you wouldn't need to invert anyway- would you?)
The only exception of the 4ths and 5ths is between F-B and B-F where our in-famous tritone intervals are lurking.
The 4th between F and B is Augmented (large) and the 5th between B and F is Diminished (small).
Invert a Diminished 5th and you get an Augmented 4th and vice versa.
This lesson is about interval inversions with "white"notes or notes without accidentals.
But it's good to know that all intervals could also become Augmented, or Diminished by using accidentals.
The best part is that even the diminished intervals become augmented and vice versa when inverted.
And you still only need to memorize how many tones (or semitones) a 2nd and a 3rd are, to compare with.
Analyze this interval:
That's an...aherrm...big interval...?
No... Invert it! And what do you get?
A # and C... A weird third.
But you know that a Major 3rd is two whole steps. This third is two semitones smaller. Still a 3rd, but a Diminished 3rd. Which makes the original interval an Augmented 6th!
That's it! No weird Intervals anymore!