Seven Chords for Every Key
When you are writing a song or chord progression it is very useful to understand your chord options. To a new player just learning about music theory this concept can seem overwhelming. Fortunately, there is a formula that can quickly help you narrow down which chord options are most likely to sound good.
There are seven chords in any given key that will sound agreeable when playing in that key. There is one chord for each of the seven notes in the major scale. The pattern of seven chords is a sequence of major chords, minor chords, and one diminished chord that are all harmonically correct in each of the 12 keys, respectively. These chords are made of notes in the scale. Therefore, they ARE the key.
The seven-chord formula is this:
I ii iii IV V vi vii
Notice that three of the chords are in capitol letters. This means that they are major chords. The lower case chords are minor chords. The vii is a diminished chord. It is a bit of a wrinkle in the pattern, but it is a great chord that has it's uses. ...So the first, fourth, and fifth chords are major, and the second, third, and sixth chords are minor. You may find a use for the seventh chord, but the first six are your common chords and they should sound familiar to the ear when played with the others. Many songs are made up of these chords. For example, the I V vi iv progression is a familiar chord progression used in hundreds of well-known songs.
Here is a video of a group of guys playing 40 songs with the I V vi iv progression:
Now that you have the seven-chord formula you can experiment with it. First, determine what key you’d like to play in. Once you’ve chosen a key you must make sure you know the notes of the major scale for that key. Then, starting with the root of the scale, follow the chord formula above to determine what chords are in the key. Here is an example:
The Key of D
D Major has the following notes: D E F# G A B C#
The chords in the key of D Major are: D Em F#m G A Bm C#dim
Try experimenting with these chords by playing them in different sequences and see what you can come up with. Then try it in another key.
As you learn and analyze the songs of other artists you can use this as a framework to understand their songs. You will see the formula at work in the music. Though many songwriters stray from this pattern from time to time most songs adhere to it. Once you know the formula and how it is used it is much easier to make sense of music that gets more exotic and deviates from it.