I introduced one of the Diminished family, the dim 7th chord, in part 1 of the Harmonic Alchemy series, "Mining for Precious Chords", and elucidated its role as a svelte non-diatonic 'chord substitution'. In this article I will take a much closer look at the 'diminished' sound and its theoretical sources.
Diminished chords are so named because of the presence of the following unique intervals i.e. their thirds & 5ths are flat (minor 3rd and diminished 5th respectively). For this reason they are often called 'minor flat 5 chords'. The diminished family includes the following chords: mb5, m7b5, m6b5 (or mbb7b5, -, dim7th), mb9b5, m11b5, mb13b5, m13b5.
These intervals create a tense dissonance and peculiar sonority. Pick through the F# mb5 below, letting the intervals ring into one another (novices are too keen to 'strum' a new find and dismiss it outright):
Notice it's strange but appealing vibe. This atmosphere is the playground of modern horror/thriller sound designers and was once where the likes of Bach and Mozart went to seek representation of anguish. Download this informative article (pdf), pages 8-17.
Now play a G major before it and an Em after
The weirdness dissipates as it slots right in, fit for purpose as a leading chord. In this way the dim chord can be used independently for its eldritch qualities, or as a team player.
The natural diatonic source for the diminished triad (R b3 b5) is the Locrian Mode because its tonic triad is diminished i.e. F# Locrian in the key of G or Em is spelled: F# G A B C D E and its tonic triad is F# A C. The interval between F# and A is a b3 and between F# and C is a b5 (also known as a tritone or augmented 4th). Note there is a b3 between the A and C so you could perceive the triad as a pair of b3rds stacked.
The b3, b5 combination also emerges by virtue of the Harmonic Minor scale. Staying in the key of Em, and sharpening D (E F# G A B C D#) reveals 3 more instances of the diminished triad- A Dorian (A C D#), C Lydian (C D# F#) and D# Mixolydian (D# F# A).
Similarly, the E Melodic Minor scale (E F# G A B C# D#) reveals a dim triad on the C# (C# E G).
The dim triad above (F# A C) is also a feature of the following scales:
1) F#m Blues: F# A B C Db E
2) F# 1/2 whole diminished: F# G A A# C C# D# E
3) F# whole 1/2 diminished: F# G# A B C D D# E
4) F# Chromatic
Here are the shapes of F# dim based on the CAGED system (note: some of these shapes require angled bars):
The dim 7th chord mentioned in the intro is a diminished triad chord extended by a 6th or bb7th (F# A C + D#). This extended dim chord also goes by the following monikers e.g. F#mb5 bb7, F#0, F# -. This is also the most common diminished chord. Indeed, most folk aren't aware of the rest of the family so I have prepared a few other extensions taken from the Locrian Mode:
The F#m7b5 is known as a 'half-diminished', which is odd considering it has an authentic diminished triad.
Here's a shortcut to a dim7 chord. If you raise the root of a dom 7th you get a dim 7th e.g. raise the F in F7 (F A C D#) to F# (F# A C D#).
In this way you can re-use the common dom7 shapes to produce dim7ths.
A dim7th chord can also be seen as an inversion of a Dom7 b9, e.g.
Refer to my previous Harmonic Alchemy articles to see how this knowledge can be used to inform chord substitutions.
I hope this article has cast the diminished chord in a favourable light and will encourage you to explore its intriguing qualities further.
Guy Pople is a music, education and multimedia specialist based in the UK`s North-West. He plays guitars, studies theory and runs St Annes Music in Lytham St. Annes, a one-stop shop for musicians on the Fylde coast of Lancashire. St Annes Music offers professional instruments, recording, tuition and accessories.
His live band Nomad is currently building up their original music. You can catch him
on Virtual Strangers.
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