Chords

So we all use chords and for a lot of us the chords come first and melody kind of falls into place, but what are chords?

To be very vague, chords are groups of three or more notes played together (harmonically). Chords can be played diatonically in which case we often call them arpeggios. We will mostly be discussing harmonic chords but most of the things we'll talk about are true for both.

A chord has a root note and two or more other notes that help determine the character of the chord. There are a lot of different chords but we'll start with the basic four for which the intervals, relative to the root note, are:

Major: root - major third - perfect fifth (CEG)
Minor: root - minor third - perfect fifth (CEbG)
Augmented: root - major third - augmented fifth (CEG#)
Diminished: root - minor third - diminished fifth (CEbGb)

All of these chords have only three notes; we call them triads when they are played with their notes in order. When we discuss triads, it's often convenient to refer to the notes as the root, third, and fifth. The root being the root note, the third the note a third above it, and a the fifth the note that is a fifth above the root. You may notice that a triad consist of three notes where the interval between a note and the one below it is a third. If we add another third on top of the top note of a triad we get a seventh chord. There are five types of seventh chords (not including fully diminished or augmented sevenths, see: http://en.wikipedia.org/wiki/Seventh_chord):

Major seventh: root - major third - perfect fifth - major seveth (CEGB)
Minor seventh: root - minor third - perfect fifth - minor seventh (CEbGBb)
Dominant seventh: root - major third - perfect fifth - minor seventh (CEGBb)
Half diminished seventh: root - minor third - diminished fifth - minor seventh (CEbGbBb)
Minor major seventh: root - minor third - perfect fifth - major seventh (CEbGB)

Now let's revisit the major scale.

In C major this looks like

C D E F G A B C

Now let's stack thirds on top of those notes to make each scale degree into a triad chord. If we do this without using accidentals, this will look like:

G A B C D E F G
E F G A B C D E
C D E F G A B C
1  2  3 4 5  6 7  1

So let's take a closer look.

1 Major triad (C major) Tonic
2 Minor triad (D minor) Supertonic
3 Minor triad (E minor) Mediant
4 Major triad (F major) Subdominant
5 Major triad (G major) Dominant
6 Minor triad (A minor) Submediant
7 Diminished triad (B diminished) Leading tone/chord

I've placed the scale degree names next to the chords as a reminder. From now on we'll be using the scale degree names and numbers interchangeably to refer to both the above chords in a key and their root notes which are the actual scale degrees.

Extending this and stacking another third on top of our major scale we get:

B C D E F G A B
G A B C D E F G
E F G A B C D E
C D E F G A B C
1  2  3 4 5  6 7  1

1 Major seventh chord (C major 7)
2 Minor seventh chord (D minor 7)
3 Minor seventh chord (E minor 7)
4 Major seventh chord (F major 7)
5 Dominant seventh chord (G major 7) Dominant seventh
6 Minor seventh chord (A minor 7)
7 Half diminished seventh chord (B half diminished 7)

We're going to talk a lot more about chords (in fact they'll be pretty much the focus of these lessons) but I just want to introduce a notation that we'll be using first.

For major keys we'll be using the following roman numerals to denote chords:

I Tonic
ii Supertonic
iii Mediant
IV Subdominant
V Dominant
vi Submediant
vii Leading tone (will be diminished without accidentals)
I Tonic

We'll use uppercase letters for major and augmented chords and lower case letters for minor and diminished chords. In addition, diminished chords will have a 'o' after the numeral and augmented chords a '+'.

In minor keys this will look like:

i Tonic
ii Supertonic (will be diminished without accidentals)
III Mediant
iv Subdominant
v (fifth)
VI Submediant
VII Subtonic
i Tonic

Notice that the fifth scale degree is not the dominant here. We'll talk about why when we discuss dominance.