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Doubly diminished third

In music theory, a doubly diminished third is an interval that has only one half step (semitone). Explanations and excerpts from famous works

In music theory, a doubly diminished third is an interval that has only one half step (semitone ).

The doubly diminished third requires that:

The interval must be a doubly diminished third interval (three note names between the first and the last).
The interval must have only one half step.

What does a doubly diminished third look like?

Here is an example of a melodic doubly diminished third (two music notes in a melody) and a harmonic doubly diminished third (in a chord):

How to recognize a doubly diminished third?

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 B / D♭♭:

Let's take the B major scale to have B as the tonic:

From the rule stated above, the interval B / D♯ is a major sixth, so the interval B / D♮ is a minor sixth, so the interval B / D♭ is a diminished sixth, and so the interval B / D♭♭ is a doubly diminished third.