Chord Substitution - Extended Chords 2
Chords can be broadly categorised into two types: those that are discords and those that are concords. Discordant chords like sevenths or diminisheds don't sound finished in themselves, but leave you with the feeling that there's more to come. Concords, on the other hand, sound harmonious and at rest.
When you move from a discordant chord to a concord, it's called a resolution. Discords create tension which is in turn resolved to a more "finished" sound.
Unless you wish to produce that unfinished effect - as in blues - you wouldn't normally finish a song on a chord that needed to be resolved. That means that usually, any substitute for the tonic chord (the chord on which songs most commonly end) should be a chord that sounds finished and complete.
Some chords which don't need to be resolved are majors, minors, sixths and major sevenths. Thus, in the key of C major, we could substitute C6 or Cmaj7 for the C chord.
But these aren't the only chords that sound complete. The major seventh can be extended into a major ninth or a major eleventh just by adding notes in thirds. The 6th chord can also be changed into a 6/9 chord.
For the purposes of chord substitution, the subdominant (IV) chord can generally be treated in the same way as the tonic (I) chord.
The dominant (V) chord of the key needs to be treated a little differently, but has a great deal of flexibility. (We'll see this in a later lesson.) You will remember from the last lesson that whereas chords I and IV become major sevenths when they're extended, chord V becomes a seventh.
If you play a seventh chord on your instrument and then a major seventh, you'll realise that they sound very different. And that's why we have to treat them differently when looking for substitute chords.
We cannot generally substitute a major ninth (etc.) for the dominant chord, but rather we must substitute extensions of the seventh.
The following table shows which chords, so far, can be substituted for a I, IV or V chord in a major key. The example, given in the key of C major, should make plain the different way the V chord is to be treated in comparison to the I and IV chords:
Understanding Scales | Understanding Chord Structure | Understanding Diatonic Chords | Understanding Minor Scales | Diatonic Chords in Minor Keys | Scale Degree Names | Chord Substitution - Extended Chords | Chord Substitution - Overlapping Chords | Improvisation - Arpeggios | Improvisation - Major Scales | Improvisation - Pentatonic Scales | Improvisation - Blues Scales