A key consists of a group of notes and the chords derived from that group of notes. A key also has one primary note and one primary chord that is build from that note. All other notes and chords are heard in relationship to this primary note/chord. This primary note is the key center, or tonal center. The group of notes that is used in a key is called a scale.

The focus of this lesson is to take a look at major keys. The key that uses the major scale as its group of notes. A key is just a flavor or color of sound. A song may stay in one key, or it may change many times throughout.

How the chords function in the key

For this lesson we are going to first look at the key of C major. As you learned in the basic chord construction lesson, the basic chords built from a C major scale are C, Dm, Em, F, G, Am, and B^o. Each chord has a function within the key. The word function just means that each chord has a unique sound in relationship to the main chord of the key. The main chord in a key is called the tonic chord, and in this case that is a C major.

To show how each chord functions in the key, Roman numerals are used as a way to both indicates the degree of the scale that a chord is built on, and the chord quality (major, minor, etc.) A Roman numeral by itself like I, IV, or V indicates a major chord. A small m after it, this means that the chord is minor. So IIm, IIIm, and VIm are all minor chords. The small circle after will indicate a diminished chord, like VII^o.

Chord functions in the key of C major

C     D     E     F     G     A     B - C major scale
|     |     |     |     |     |     |
C     Dm    Em    F     G     Am    B^o - Chord Name
I     IIm*  IIIm  IV    V     VIm   VII^o - Function

*Traditional classical theory uses a lower case Roman numeral to indicate a minor chord function....ii, iii, vi. And the small m is not used. It more modern theory...Jazz, Rock, and other contemporary music, chord functions use capital Roman numerals. Then a small m is used if the chord is minor, a small circle is used for diminished, and there are other modifiers as well that will tell you what the quality of the chord is. (Ex. IIm, IIsus2, II7)

The harmonization (creation of chords or harmony) of a major scale will always follow the same pattern, no matter what major key you are in. The basic chord build on the 1st degree of the scale is major, the 2nd is minor, the 3rd is minor, the 4th is major, the 5th is major, the 6th is minor and the 7th is diminished.

Page 2, Basic chords and functions in all of the major keys