Guitar Chord Numbering System

The guitar chord numbering system in use in most circles names one of the 12 tones the One (I), and the 2-7 are determined by that tone chosen as the one.

In Western music, the I, IV, and V chords are the most important and common chords that are utilized. The I chord is also called the Tonic. The IV chord is also called the Subdominant. The V chord is also called the Dominant.

Tonics like to move to Subdominants. Subdominants like to move to Dominants. Dominants like to go to Tonics. When chords follow this progression ( I to IV to V to I), this is considered progressive harmony (regressive being the reverse).

Progressive Harmony looks like this...

Why is the Subdominant named such?

The subdominant is called such because it is the dominant below (5 tones below), not because it is one under the Dominant.

Next, the tonic, subdominant, and dominants in the keys of C, G, D, and A. These chords are triads (3-note chords).

These chords can be used for any style, but keep in mind these voicings aren't fully bluesy (need flat 7 to get the blues sound).

Particular styles use particular voicings. The voicings below are perfect for folk, country, rock ballads, etc.

Tonics (I), Subdominants (IV), and Dominants (V)

There are many more ways to play these chords.

These are starter chords (triads) for blues progressions (substitute the triad for the 7th chord, ie. C for C7).

Next, the I, IV, V for all keys. Guitar chord numbering is a great way to keep track of relationships between chords. It is important to memorize (move information to pure knowledge) the relationships between chords.

C is always G's IV, using this numbering system.

Again, practice playing the blues progressions substituting these triads for the I, IV, and V.

And, memorize the relationships, starting with C, G, D, and A.

Apply guitar chord numbering in all keys (I ii iii IV V vi viio)