There are just a couple more chord flavors to talk about before moving on to other topics. We'll first learn about the other two kinds of triads: Augmented and Diminished, and then we'll have a look at 6^th chords. These are fairly uncommon flavors, so don't get too hung up on them at this stage, but like all chords, they can just be seen as altered major chords.

We have already touched on Diminished Chords in the 'Chords defined' page. We learned that one of the diatonic chords (chords that arise naturally from the major scale) is a half-diminished chord, better know as 'minor seventh flat five', or m7^thb5. That name already says 'diminished' because the Perfect Fifth has been flatted by one semitone. So the diminished triad is 1-b3-b5 ... both the third and the fifth have been flatted (or diminished) by a semitone. There is also another kind of diminished, one that has a 'double flat seven' note thrown in, which is a fancy way of saying '6'.

There's no need here to go into the reason why it's called 'bb7' instead of 6, but this chord is sometimes called 'Diminished 7^th', or 'Full Diminished' or even 'Fully Diminished'. The constituent notes of a Dim7 chord are 3 semitones apart, so it has the same quirk as augmented chords: there are, in effect, only 4 diminished chords, since the inversions of any given one are three frets apart. 12 divided by 3 equals 4. Below are the most common shapes for Diminished chords. Let's start with the 'Half Diminished', better known as the 'Minor seventh flat five' chord.

Half Diminished or 'm7^thb5 chord shapes | 1 - b3 - b5 - b7

These are played as four-note chords.

These are also played as four-note chords. Notice that the flat seven has been flatted, making it a double flat 7. Crazy, but true.
The nice thing about full diminished chords is that you can move either of these
two shapes up or down the fretboard by three frets and you will be playing the very same chord in a new inversion.

Augmented Chords

We learned long ago that major chords consist of the 1-3-5 of the major scale and that minor chords consist of the 1-b3-5 of the major scale (everything relates back to the major scale, even minor chords). Augmented chords consist of 1-3-#5 ... so the interval called the 'Perfect Fifth' has been 'augmented', or raised by one semitone. These chords have a very unstable sound because of that and are therefore not very common and are used as passing chords more than anything else, chords that lead from one stable chord to another.

The one interesting thing about them is that the intervals between the three notes are equal: four semitones (a major third is the proper term) between each note. What that means in practical terms is that there are in effect only 3 augmented chords, not 12. That's because augmented chords have inversions just as any chord, and because the constituent notes are four frets apart, the next inversion for each chord is four frets away. 12 divided by 4 equals 3. The video above lets you hear and see all of that in action. Below are the main shapes for Augmented chords.

Move either of these shapes up or down 4 frets and you have a new inversion of the same chord.
This means, in effect, that there are only three augmented chords!

Sixth chords (6th)

6^th chords (Major) | 1 - 3 - 5 - 6

6th chords (minor) | 1 - b3 - 5 - 6