What is a key?
Concept
A key is the set of 7 notes a song mostly uses. In the key of C major, those notes are C D E F G A B. From those 7 notes you can build 7 chords. That's why so many songs in C use C, G, Am and F.
Where the 7 notes come from
Take the major scale formula W-W-H-W-W-W-H and apply it to a root. Starting on C: C D E F G A B. Those are the 7 notes of the C major key. Starting on G with the same formula: G A B C D E F#. Same shape, different notes.
Why this is useful
If you know a song is in the key of C, you can predict that: - The melody mostly uses C D E F G A B (rarely accidentals). - The chords are mostly built from those same 7 notes. - The chord at the end of the song is probably C — the 'home' chord.
That's why two songs in the same key often share chords. It's not a coincidence; they're drawing from the same pool.
Home base — the tonic
The first chord of the key (C in 'C major') is called the tonic. It's the chord everything resolves to. Most songs in a key start and end on the tonic. When you hear a song 'finish,' that's usually the tonic landing.
Key takeaways
- •A key = a set of 7 notes and the chords built from them.
- •The tonic is home base; songs usually end there.
- •Knowing the key tells you which chords will sound 'right.'
Glossary
- Key
- The tonal center of a song — the set of notes and chords it draws from.
- Tonic
- The 'home' note/chord of a key. The 1st degree.
- Accidental
- A note outside the current key, marked with a sharp, flat, or natural.
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