Diminished

What it means

An interval is called diminished when it is reduced by a semitone relative to its perfect or minor form, without the degree count changing. The perfect fifth becomes the diminished fifth, the minor seventh the diminished seventh, the perfect fourth the diminished fourth. All diminished intervals are dissonant.

In the notation

The reduction can be read only from the accidentals, since the degree count stays the same. This is not a shortcoming but the point: the spelling fixes which degrees are meant and where the notes go. Diminished intervals draw together — the lower note rises, the upper falls — while augmented ones strive apart. Sonically identical intervals can therefore call for opposite continuations.

Musical use

The most important case is the diminished fifth, which together with the augmented fourth forms the tritone and lies, in the dominant seventh chord, between the third and the seventh. From it results the diminished triad on the seventh degree in major, and from stacked minor thirds the diminished seventh chord, which divides the octave evenly and therefore has no unambiguous root — a circumstance that makes it especially useful for enharmonic reinterpretation and remote modulations. The half-diminished seventh chord is the softer form, with a minor rather than a diminished seventh.

In inversion, a diminished interval becomes an augmented one.

An interval becomes diminished through the reduction of a perfect or minor interval by a chromatic semitone. In this way arise, for instance, the diminished fifth from the perfect fifth, and the diminished seventh from the minor seventh. Diminished intervals often sound like other intervals — the diminished seventh, for instance, like the major sixth — but strive inward: their notes move toward each other upon resolution. In chord symbols, “diminished” stands for triads and seventh chords built from minor thirds.

Performance practice

Watch the direction of the resolution: diminished intervals close. With flexible intonation, take the lower note rather high and the upper rather low, so that the pull becomes audible. And check the spelling before you shape a passage — it says more about the continuation than the sound does.