Chord Construction - 7th Chords

 

An earlier tutorial described how the basics of chord construction, and introduced the concept of three note chords called triads. If you're comfortable with the theory covered there, then you shouldn't find this to be too much of a struggle.

Just as triads are built by taking alternate notes from a parent scale, this process may be extended so that the 7th note of the scale is included in the chord, along with the 1st, 3rd and 5th. For example, consider C major:

This process can be repeated using the other notes of the parent major scale as root notes, and building on these with alternate notes from C major (the parent major scale). As with triad construction, notes in the chord should be diatonic to the parent majpr scale, so there will be some flattening of notes required. When this has been done for all the scalar degrees, we have a set of seven 7th chords:

Take a look at some of the chord types here:

Chord Name Also Written as Notes Formula
C7 "C Major 7" CM7, C Maj 7 C, E, G, B 1, 3, 5, 7
Dm7 "D Minor 7" D min 7 D, F, A, C 1, b3, 5, b7
Em7 "E Minor 7" E min 7 E, G, B, D 1, b3, 5, b7
F7 "F Major 7" F M7, F Maj 7 F, A, C, E 1, 3, 5, 7
G7 "G Dominant 7"
or "G7"
  G, B, D, F 1, 3, 5, b7
Am7 "A Minor 7" A min 7 A, C, E, G 1, b3, 5, b7
Bø7 "B Half-Diminished"
or "B Minor 7 flat 5"
Bm7b5 B, D, F, A 1, b3, b5, b7

When a major scale is harmonised in 7th chords, there are types of chord, namely major 7, minor 7, dominant 7 and half-diminished.Each of these has its own distinctive sound - in particular notice that although the dominant 7 chord sounds distinctly different to the major 7 chord type, it still retains a certain "major-ish" sound due to the major triad on which both chord types are built.

It's also important to point out that the 7th chord on the seventh degree of the scale is called 'half-diminished', although it's built on a diminished triad. The reason that the 7th chord is called 'half-diminished' rather than 'diminished' or 'fully-diminished' will come clear later - in the meantime, just note the correct naming convention here (and the use of the ø symbol meaning 'half-diminshed').

Take the time to get to grips with the theory behind all of this. Elsewhere, I've provided some useful fingerings for chord shapes for these chord types, as well as some reference charts showing all of the major scales harmonised in 7th chords. As an exercise, try harmonising out some other major scales as 7th chords and check your results against the reference charts. Best of luck.


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