La séquence II-V-I

Lesson on Chords in the Key of C

Alright, in this lesson, we're going to switch to the key of C, a nice, friendly key.

Understanding Chord Relationships

We're going to talk about how these chords, the seven chords in the key, relate to each other. The most important set of chords you'll come across in jazz is the ii - V - I or the perfect cadence.

The Perfect Cadence

• A perfect cadence is just V - I, which means G7 to C major.
• If they're seventh chords, it'll be C major seven, not just a triad: G7 to C major seven.

Adding the ii Chord

It's really common to put a two chord in front of that:

• The two chord is D minor, which makes it:
  • D minor - G7 - C major 7

This is probably the most common chord sequence in most Western music, at least in jazz.

Practice in Different Keys

You should practice that in different keys, keeping in mind that those three chords all come from the same scale.

• Think of the scale of C as a continuous continuum up the keyboard, including all the notes needed to play over those chords.
  • If you start the scale on D, it fits D minor.
  • If you start it on G, it fits G7.

Understanding Modes

• The D minor is called the Dorian mode (F natural, C natural).
• The G7 is called the Mixolydian mode (F natural).

You might ask:
"Why do I need to know those modes?"

It's true that you can play just using white notes over a 2 - 5 - 1, especially with patterns that keep moving. However, if you want to play in a more bebop or jazzy style, you should think about how what you play fits those chords.

Chord Inversions

Let's get to grips with these chords in their different inversions.

1. Root Position D minor: Start with this as the most straightforward way.
2. Keep the bottom two notes of D minor and play G7 second inversion.
3. Then, keep the top two notes there; that becomes C major 7.

Practicing Other Inversions

You need to be able to do this in other positions as well:

• First inversion: D minor 7, G7, C major 7.
• Second inversion G7: This would be root position, C major, second inversion again.
• Third inversion: Starting with the seventh on the bottom, D minor to G7, first inversion back to third for C major.

Observing Patterns

Notice that the 1, 2, and 1 chords generally have the same inversion. You're moving back to it with a different shape in the middle, like:

• Root, two root
• Or 1, 3, 1
• Or 2, root, 2, 3, 1, 3.

Completing the Routine

By practicing this little routine in the four different positions, you've covered every possible inversion of all three chords.

Analyzing the Perfect Cadence

Let's look at how the roots of those chords move in a perfect cadence.

Root Movement

We're talking about moving from G to C:

• This indicates moving from dominant to tonic.
• The root moves up a fourth, as dominant chords tend to resolve that way, from V to I in a perfect cadence.

The ii - V - I Relation

Now, with the ii - V - I:

• The roots are still moving up in fourths, but we's starting on two.
  • D up a fourth to G, and then up to C again, minor to dominant to major.

Spotting a 2 - 5 - 1

To recognize a 2 - 5 - 1:

• Look for roots moving up in fourths.
• Ensure the chords move from minor to dominant to major.