A diminished chord is one of those things you come across when you’re learning guitar which seems way more complicated than it is. Theory-phobics would understandably turn tail and run at the sight of a chord like Bm7b5 or when asked to switch out the fifth with a diminished seventh, but it really isn’t as hard as it seems. Plus, players such as Steve Vai, Django Reinhardt, Frank Zappa and Yngwie Malmsteen have made use of them, and they’re common currency for blues and jazz players. Learning how they’re put together, how to play them and how you can make use of them in your playing can add a whole new level of depth and complexity to your compositions.

The Theory

Diminished chords are basically built on consecutive minor thirds. So if the root is C, then Eb would be a minor third above it, and Gb would be a minor third above that. This means that the formula for a diminished chord is I (root), bIII and bV, and if you’re playing a diminished seventh chord, you simply add another minor third interval on the top. For music theoryrelated reasons, this chord is technically referred to as a bbVII, despite the fact that it is actually the VI note. In C, for example, the bbVII would be Bbb, which would much more simply be referred to as A. There are actually only three distinct diminished seventh chords, because one note isn’t obviously dominant in the chord and the same patterns repeat; an Eb diminished seventh has all of the same notes as the C diminished seventh (Eb, Gb, A, C), as do the A and Gb versions of the chord. You can also have a half-diminished chord, which just includes the bVII instead of the double-flat. This formula corresponds to a minor (bIII) seven (bVII) flat fifth (bV) chord, like the scary-looking Bm7b5 in the introduction.

Moveable Diminished Shapes

Since diminished seventh (dim7 or °7) chords have repeating patterns – and the vast majority of diminished chords you’ll play on the guitar are this variety – you can get by with just three chord shapes. These are moveable in the same way as barre chords, except that each one repeats in a different voicing when you move it up three frets. Here are the three shapes you’ll need to play dim7 chords on the D, A and E strings.

diminished chords

It is important to remember that from a technical standpoint moving any one of these chord shapes up by three frets produces the same chord but with the root in a different place. If you imagine the upper fret on these diagrams is the first fret, then the chords are Edim7, Bdim7 and F#dim7 from left to right.

Similarities to Dominant Sevenths

The actual notes in a diminished seventh are surprisingly close to dominant seventh chords, so it’s very easy to modulate between keys using them. For example, if you fret the Edim7 shown above, you can switch to a D#7, A7, C7 or an F#7 by moving any individual note one fret lower. Switching the E on the D string to the first fret makes D#7, if you move the A# (on the G string) down to A you get an A7, if you move the C# on the B string down you produce a C7 chord and moving the G on the high E string down gives you an F#7. The same goes for any diminished seventh chord, adding a vital key-changing tool to your arsenal.

How to Use Them

Aside from modulations, there are a couple of common ways to build diminished seventh chords into your chord progressions. Thanks to their similarity to dominant sevenths, you can use a diminished seventh in their places in a chord progression. The dominant seventh works to bring about a “cadence” – or a sense of “ending” – and the diminished seventh accomplishes the same thing with an especially tense feeling. Play the dim7 version of the VII chord in the specific scale (Bdim7 in C) in its place, because the notes are almost the same as the V7 chord (in C: G7 = G, B, D, F and Bdim7 = B, D, F, Ab).

A final idea is to lead into a chord with a diminished seventh chord that is half a step below it. For example, even a simple C, F, G, C progression can be spiced up if you add an Edim7 before the F, a F#dim7 before the G and a Bdim7 before going back to the C.

Conclusion

They might give rise to some terrifying looking chord names, but diminished chords have a lot to offer to guitarists with an interest in songwriting, especially budding jazz and blues composers. Regardless of your genre, the unique effect of diminished chords can really bring a sense of tension and release to your music – so do some experimenting!

About The Author

Founded in 1998, Guitar Tricks was the Web’s first multimedia guitar lesson site. 15 years later, Guitartricks.com features over 40 guitar instructors continuously creating a massive library of online video guitar lessons (8000+) covering every musical style, technique, and level of ability. John has played guitar for several years and is excited to contribute his and Guitar Tricks’ knowledge to this blog!