The chords in a key
A free guitar lesson · 5 steps · about 8 minutes
A chord on every note
Build a chord on each of the seven notes of a major scale, using only notes from that scale, and you get the seven chords of the key. They always follow the same pattern of major and minor:
- chords 1, 4 and 5 are major;
- chords 2, 3 and 6 are minor;
- chord 7 is diminished, a tense chord you will rarely need on its own.
Musicians number them with Roman numerals: capitals for major, small letters for minor.
The key of C
C, F and G are the three major chords. Dm, Em and Am are the minors. Almost every song in C uses chords from this row, which is why C, F, G and Am go together so naturally.
The key of G
Same pattern, different chords: G, C and D are major; Am, Bm and Em are minor. Now you can see why the G, C and D progression from the open-chords section works so well. It is the I, IV and V of G.
Progressions are numbers
Because the pattern is the same in every key, songs are really patterns of numbers. Two of the most famous:
I - IV - V - I G - C - D - G (folk, country, rock and roll) I - V - vi - IV G - D - Em - C (a huge share of modern pop)
Learn a progression as numbers and you can play it in any key: just look up the chords in that key's row.
Working out a song
Next time you hear a song, try this. Find the home chord first, the one it keeps returning to and ends on. That is chord I, and its name is the key. Then try the other chords from that key's row, one at a time, until they fit. You will be surprised how often the answer is only three or four of them.
OnPitch shows the detected key and chords when you analyse a song, so you can check your guesses against it.