Guide to Diminished Chords: How to Play Diminished Chords

Diminished chords are triads that include a root, a minor third, and a flat fifth (also called a diminished fifth). Their first two notes are the same as those in a minor triad—the difference is the fifth. In a minor chord, the fifth is natural, which means it is a perfect fifth above the root pitch. In a diminished chord, the fifth is dropped down by a half step to a tritone above the root note.

Diminished triads naturally occur when building a chord from the seventh degree of a major scale. For instance, in the key of C major, the seventh scale degree is the note B. Using only the notes of the C major scale for your chord tones, you can create a triad starting on B. The notes will be B (the root), D (the minor third), and F (the diminished fifth); those three pitches combine to make a B diminished chord. In this instance, B is the leading tone of the C major scale because it leads back to C. Thus, a B diminished chord is the leading-tone triad of C.

Diminished seventh chords are diminished triads with a seventh added. Sometimes the seventh is an upper voice of the chord, but it can appear anywhere in the chord structure (although it's rare to hear the seventh as the lowest pitch in a diminished seventh chord).

There are two kinds of diminished seventh chords:

1. 1. Diminished chords with a flat seventh: In popular music styles (particularly jazz), these chords are called "minor seventh flat five” chords. In classical music, they're called "half-diminished" chords. They contain a root, a minor third, a diminished fifth, and a flat seventh. For instance, the chord C minor seventh flat five—also written Cm7(b5)—contains the pitches C (the root of the chord), E (the minor third), G♭ (the diminished fifth) and B♭ (the flat seventh). It has the same chord tones as a C minor seventh chord, only with the fifth a half step lower. Minor seventh flat five chords are fairly popular as guitar chords, particularly in jazz music and progressive rock.
2. 2. Diminished chords with a double flat seventh: These chords, usually just called "diminished seventh chords" (or dim7 chords) contain a root, a minor third, a diminished fifth, and a diminished seventh. To get a diminished seventh chord tone, you simply lower a flat seventh by a half step. Using the previous example, you can turn the Cm7(b5) into a Cdim7 chord by simply lowering the B♭ (a flat seventh) to B♭♭ (a diminished seventh). Note that B double flat is the same pitch as A natural.

Sometimes the "degree" symbol is used to notate diminished chords in sheet music books. Therefore, a Bdim7 chord might appear as Bº7, depending on who wrote the chord chart.

Diminished chords can be surprisingly useful in all styles of music. They fit well in both major keys and minor keys, provided you use them properly. Consider these tips for working diminished chords into your own songs:

• Use them as passing chords. When playing a chord progression, you can lead into a major chord by approaching it from the diminished chord a half step below it. For instance, if you're planning to play a G major chord, precede it by briefly playing F#dim7 chord. You'll create a jazzy effect with the dissonant chord. All notes then move up a half step to the G major chord.
• Use them in place of dominant chords. The dominant chord in both a major key and a minor key is the V chord. You can substitute a diminished chord for the V chord by using a dominant function. For instance, in the key of D major, the V chord is A7, with the notes A-C♯-E-G. The upper structure of that chord (C♯-E-G) happens to be a C# diminished triad, ao instead of playing A7, try playing a C#dim triad or a C#dim7 chord for a more complex sound.
• Play multiple diminished chords in a row. If you want to create a spooky sound, try playing several diminished chords one after another. Keep the chord shape the same and move your hand up and down your piano keyboard or guitar neck so that all the pitches move in parallel motion, creating an eerie mood.

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