In music theory, a doubly augmented sixth is an interval that has eleven half steps 
The doubly augmented sixth requires that:
- The interval must be a sixth interval (six note names between the first and the last).
- The interval must have eleven half steps.
What does a doubly augmented sixth look like?
Here is an example of a melodic doubly augmented sixth (two music notes in a melody) and a harmonic doubly augmented sixth (in a chord):
How to recognize a doubly augmented sixth?
Rule of music theory: All intervals in a major scale starting with the tonic (degree I) are either major or perfect, and only unison, octave, fourth and fifth are perfect (the others are major).
Example with the interval C / A♯♯:
Let's take the C major scale to have C as the tonic:
From the rule stated above, the interval C / A is a major sixth, so the interval C / A♯ is an augmented sixth, and so the interval C / A♯♯ is a doubly augmented sixth.
Inversion of the doubly augmented sixth
The inversion of the doubly augmented sixth is the doubly diminished third.
Here is an example of a doubly diminished third:
Musical examples of doubly augmented sixth
No examples yet, but feel free to send me some examples!
Interval identification game
You will find this interval in my Intervals identification game:
