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7 Diminished seventh

Diminished sevenths create extra colour and direction to a chord progression by creating tension that then resolves to a diatonic chord (often but not always the dominant). Diminished sevenths always to a chord a semitone above their root so in the example below the F# diminished seventh resolves to ii (G minor) and the B diminished seventh eventually resolves to C (with a 6/4 in between).

Mozart Piano Sonata in Bb K. 333, first movement

dim 7 mozart

How to write diminished sevenths

dim 7 instructions

  1. decide on the chord to which your diminished seventh will resolve
    in this example an E major chord (V of A major)
  2. write down the note below the root of this chord
    in this example D – one note below E
  3. then add a sharp or a natural if necessary so that it is a semitone below the note it will resolve to
    in this example add a sharp to the D
  4. add three thirds above the root of your diminished seventh
                in this example, F#, A, C#
  5. add appropriate accidentals to ensure that each third is a minor third
    in this example, you need to change the C# to a C natural
    the root note of the diminished seventh must resolve up a semitone and the seventh should resolve down, as in the example (i.e. if a violin had the C natural it should follow it with a B)