Chord Study 5 - Augmented 5th and Diminished 7th

Augmented 5th Chord

An augmented 5th chord is written with aug or aug5 after the key: Aaug, Gaug, Faug5, Caug5. It is formed by raising the 5th note of the scale by one fret in a major chord. Sometimes this chord is also written with + or +5 after the key.

In C major scale, G is the 5th note and raising it by one fret becomes G#.

See how the 5th note was raised by one fret while raising also its equivalent note in the higher octave. F is the augmented 5th of the A major scale.

Diminished 7th Chord

This chord is formed by lowering all the notes of the dominant 7th chord by one fret except for the 1st note of the scale. It is often written with "dim" after the key like Adim, Ddim, Gdim and etc.