7th chords are built from TRIADS and are the chords most people associate with a fuller, richer sounding harmony. They are extremely common in modern music and are pretty much a requirement for anyone serious about bolstering their musical chops.
Of primary importance are the following types of 7ths:
And because 7ths are built from TRIADS, I’m going to use the same graphics that were used with TRIADS to show the newly created 7ths. The thing to really understand when looking at the following graphics is that each of them is created from varying combinations of stacked 3rds.
MAJOR 7th chord
The MAJOR 7th chord is a MAJOR triad with an added vii scale degree.
MINOR 7th chord
This is the minor triad with an added vii scale degree that’s been flattened.
minor 7b5 chord
The makeup of the minor 7b5 (flat 5th) chord should be fairly obvious after looking at the minor 7th chord above. You simply take the minor 7th chord and flatten its 5th degree.
This chord is often referred to as a half diminished 7th.
minor MAJOR 7th chord
A minor MAJOR 7th chord can be thought of as a cross between a MAJOR 7th chord and a minor 7th chord. It’s basically a MAJOR 7th chord with a flattened iii scale degree.
DOMINANT 7th chord
A dominant 7th chord is nothing more than a MAJOR 7th chord with a flattened vii scale degree. This popular (and important) chord has a very strong attraction to the MIXOLYDIAN mode because they both share a flat 7 scale degree.
This chord is also sometimes referred to as a Major Minor 7th because it has a minor 7th but also has a MAJOR 3rd. It’s a little odd to have to think of anything ‘minor’ scale degree (note) as being Dominant, but that’s the case as far as the 7th scale degree of Dominant chords is concerned.
DIMINISHED 7th chord
The Diminished 7th chord is the same as a minor 7th chord with a flattened V degree and a diminished vii degree.
AUGMENTED 7th chord
An Augmented 7th chord is kind of a strange chimera of a chord in that it has a MAJOR 3rd combined with a sharpened V degree and a flattened 7th degree. It feels like it’s being pulled in different directions and often sounds like it as well. It’s easiest to remember this chord by thinking of it as a DOMINANT 7th with a sharpened 5th scale degree (V#).