Diminished piano chords are not the most common type of chord but they do add something interesting to a chord progression when needed.
Here I'll explain both how diminished chords are made and also provide a (pinable) list of all the diminished chords.
Diminished chords are made this way: start with a major chord. For example, C major – C E G. To make it diminished you lower the 3rd and 5th notes of the scale. In our example’s case, that would be the C major scale.
Lowering a note means to make it lower by a semi-tone or half-step. This usually means going from a white key to the next lowest black key or vice versa. For example, E goes to Eb, C# goes to C. Be careful of C and F though because with these notes you go to the next lowest white key.
To make a C diminished chord, you must lower E to Eb and G to Gb. Altogether, the chord is C Eb Gb. A diminished chord is written like this: Cdim or Co (with the "o" being set up high in line with the top of the C, not low like you see here).
Here’s a list of the diminished chords:
Cdim / C° = C Eb Gb
C#dim / C#° = C# E G
Dbdim / Db° = Db Fb Abb
Ddim / D° = D F Ab
Ebdim / Eb° = Eb Gb Bbb
Edim / E° = E G Bb
Fdim / F° = F Ab Cb
F#dim / F#° = F# A C
Gbdim / Gb° = Gb Bbb Dbb
Gdim / G° = G Bb Db
Abdim / Ab° = Ab Cb Ebb
Adim / A° = A C Eb
Bbdim / Bb° = Bb Db Fb
Bdim / B° = B D F
Some of these chords have double flats. That means that you take the note that already is a flat, and make it lower by an additional semi-tone. For example, Bbb (double flat) will actually be an A on the piano.
Diminished chords are not very common. If you need to know a specific chord, just remember to lower the 3rd and 5th notes. You can also go and find the specific chord when you come across it.
The cool thing about diminished chords is that they are made up of minor thirds.
A minor third is an interval - a space between 2 notes.
C to Eb is an example of a minor third in music. On the piano, you can see that there are two semi-tones between C and Eb, Db and D. This is the same for every minor third.
D and F are a minor third apart. That means you skip Eb and E - the 2 semitones.
To figure out any diminished chord, you just need to play notes a minor third apart.
For a diminished chord this means:
Root note - up a minor third - up a minor third.
Example: C - up a m3 to Eb - up a m3 to Gb.
Diminished 7th chords are very similar to diminished chords, all you do is add another minor third on top of the one you already have.
Diminished 7th chords are made this way:
Root - up a minor 3rd - up a minor 3rd - up a minor 3rd.
Cdim7 = C Eb Gb Bbb (double flat)
As you can also see from the example above, diminished 7ths have the chord title of dim7 or °7.
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Diminished piano chords are used a number of ways:
Classical Music: Composers like Beethoven, Chopin, and Wagner employed diminished chords to create dramatic effects and facilitate modulations.
Jazz: Diminished chords, especially diminished seventh chords, are staple ingredients in jazz harmonies, often used as passing chords or to add color to progressions.
Pop: While less common in pop, when used, they often lend a unique and unexpected twist to an otherwise predictable chord progression.
If you want to learn more about chords and how to make the different kinds, check out the chord theory page.
You can also find more chords on the chord charts page. This is about all there is to diminished piano chords. They sound complicated but once you understand them, they’re easy!