A Diminished Triad: The Complete Guide 🎸🎹🎶

By Jade Bultitude
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In this article, you’ll learn how to construct the A diminished triad as well as how to play it on piano and guitar.

We’ve also included sections on inversions for those that want a deeper understanding. Lastly, listen to some examples of popular songs that featured this triad.

Root, 3rd and 5th

The A dim triad is formed of the 1st, flat 3rd and flat 5th of the A major scale.

  • A – root note
  • C – Minor 3rd above the root
  • Eb – diminished 5th above the root

Here is the triad written on the stave in the treble and bas clef.

A dim triad treble clef
A dim triad bass clef

Before you read on make sure that you have a basic understanding of intervals. Intervals are vital for understanding how triads are built. Check out our guide to major, minor and perfect intervals for more on this.

A diminished Chord on Piano

Below you can see how to play this triad on the keyboard or piano. This pattern of notes could also be played starting on any A note.

However, the order of the notes must be the same:

  • A – lowest note
  • C – middle note
  • Eb – highest note

This is called ‘root position’.

A diminished chord root position piano diagram

A dim Triad on Guitar

There are two simple positions that you can use to play an A dim chord on guitar. Both positions can also be slide up or down the neck to play different diminished triads.

A diminished chord root position guitar chart

1st Inversion

A 1st inversion is where we take a triad but we start on the second note, which in this case is C natural. We still keep the E flat above, but then the A (or root) become the highest note.

  • C – min 3rd (lowest note)
  • Eb – dim 5th (middle note)
  • A – root note (highest note)
A diminished chord 1st inversion

1st inversion on Piano

On the piano we can play the 1st inversion of an A dim triad by starting on a C natural. They play the Eb above and the A above this.

A diminished chord 1st inversion piano diagram

1st Inversion of Guitar

Below are the most common shapes for playing an A diminished triad in the 1st inversion. Remember that we can only use certain shapes are the pitches of the three notes are important.

A dim triad 1st inversion guitar chart

2nd Inversion

A 2nd inversion is where we take a triad but we start on the third note, which in this case is E flat. We still keep the A above this as we did from the 1st inversion. Then the C becomes the highest note in the chord.

  • Eb – dim 5th (lowest note)
  • A – root note (middle note)
  • C – min 3rd (highest note)
A dim triad 2nd inversion

2nd inversion on Piano

On the piano we can play the 2nd inversion of an A diminished chord by starting on a E natural. They play the A above and the C above this.

A diminished chord 2nd inversion piano diagram

2nd Inversion of Guitar

Below are the most common shapes for playing an A dim triad in the 2nd inversion. Remember that we can only use certain shapes are the pitches of the three notes are important.

A diminished chord 2nd inversion guitar chart

Keys that Include A Diminished Triad

You might be asking – what key do you find A dim triad in? Well, as you can see below, A Dim is the second chord in the key of G minor.

chords in g minor

It is also the 7th chord in the key of Bb Major.

chords in b flat major

What’s next….? 

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AUTHOR
Jade is a flute player and music educator with a passion for educating the next generation of musicians. She is a Masters Graduate from Trinity Laban Conservatoire of Music and Dance. Jade has been helping people learn music theory for more than 10 years from pre school children all the way to degree level studies.