In music theory, a augmented second is an interval that has three half steps 
The augmented second requires that:
- The interval must be an second interval (two note names between the first and the last).
- The interval must have three half steps.
What does a augmented second look like?
Here is an example of a melodic augmented second (two music notes in a melody) and a harmonic augmented second (in a chord):
How to recognize a augmented second?
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 / D♯:
Let's take the C major scale to have C as the tonic:
From the rule stated above, the interval C / D is a major second, so the interval C / D♯ is a augmented second.
Inversion of the augmented second
The inversion of the augmented second is the diminished seventh.
Here is an example of a diminished seventh:
Musical examples of augmented second
For music lovers accustomed to western tonal music, the augmented second immediately sounds oriental:
Hava Nagila
Hava Nagila is a Hebrew folk song that features a few augmented seconds:
Interval identification game
You will find this interval in my Intervals identification game:
