The notes of the harmonic minor scale are the same as the natural minor except that the seventh degree is raised by one semitone, making an augmented second between the sixth and seventh degrees. The sequence of steps: "Whole:Half:Whole:Whole:Half:Whole-and-a-half:Half" (in semitones: 2 1 2 2 1 3 1).

Harmonic minor scale: 1 2 ♭3 4 5 ♭6 7 8

The scale is so named because is a common foundation for harmonies (chords) used in a minor key. For example, in the key of A minor, the V chord (the triad built on the note E) is normally a major triad that includes the raised seventh degree of the scale: G♯, as opposed to the unraised G♮ which would make a minor triad.

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Chords on degrees other than V may also include the raised seventh degree in minor keys, such the diminished triad on VII itself (vii^o); and also the augmented triad on III (iii⁺), which is not found in any "natural" harmony (that is, harmony based on notes of the major scale only, or the natural minor scale only). This augmented fifth chord (♯5 chord) played a part in the development of modern chromaticism.

The inversions of an augmented triad introduce no intervals (allowing for enharmonic equivalents) that are absent from its root position. The first inversion is enharmonically equivalent to a new augmented triad in root position. For example, the triad E♭–G–B in first inversion is G–B–E♭, enharmonically equivalent to the augmented triad G–B–D♯. The same is true for the second inversion. One chord, with variously spellings, may therefore have various harmonic functions in various keys, which introduces ambiguous tonality and opens the door to chromatic possibilities exploited by J. S. Bach, for example, and of course by many later composers. A similar analysis applies to the diminished seventh chord, founded on the diminished triad on VII in minor keys and ambiguous for the same reasons as the augmented triad.

While it evolved primarily as a basis for chords, the harmonic minor with its augmented second is sometimes used melodically. Instances can be found in Mozart, and notably in Schubert (for example, in movement 1 of String Quartet 14, "Death and the Maiden"). In this role it is used descending far more commonly than ascending.

The harmonic minor is also occasionally referred to as the Mohammedan scale^[1] as its upper tetrachord corresponds to the Hijaz jins, commonly found in Middle Eastern music. The harmonic minor scale as a whole is called Nahawand-Hijaz^[2] in Arabic nomenclature, and as Bûselik Hicaz ^[3] in Turkish nomenclature. And as an Indian raga it is called Kirwani.

The Hungarian minor scale is like the harmonic minor scale but with a raised fourth degree. This scale is sometimes also referred to as "Gypsy Run", or alternatively "Egyptian Minor Scale", as mentioned by jazz legend Miles Davis who describes it in his autobiography as "something that I'd learned at Juilliard".^[4]

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