This is an often-asked question. And it is surprising how many wrong answers there exist on the Web. Let's clarify this issue.
There are 12 keys. Wrong!
Someone says that there are 12 keys. As an octave is composed of 12 half-steps (or semitones), it's easy to get misled and think that we can build 12 major scales starting from each of those notes and get 12 keys.
Sure, but there are more than 12 keys.
There are 24 keys, we have to include minor keys. Wrong!
There are more than 12 keys, because we have to consider also minor keys! This doubles up our count, and so there are 24 keys. But this is wrong as well...
Let's see how many keys actually there are
Let's start with simple considerations.
We have 7 notes:
Then we have sharp notes and flat notes. Let's count how many keys we can create by adding those sharps and flats.
We can have a major key without sharps and flats: C major.
- We can have a major key with 1 sharp
- We can have a major key with 2 sharps
- We can have a major key with 3 sharps
- We can have a major key with 4 sharps
- We can have a major key with 5 sharps
- We can have a major key with 6 sharps
- We can have a major key with 7 sharps
- We can have a major key with 1 flat
- We can have a major key with 2 flats
- We can have a major key with 3 flats
- We can have a major key with 4 flats
- We can have a major key with 5 flats
- We can have a major key with 6 flats
- We can have a major key with 7 flats
How many major keys are in total?
1 (no sharps and flats) + 7 (sharps) + 7 (flats) = 15 major keys
As minor keys are relative to major keys, we have 15 minor keys as well. 15 + 15 = 30
There exist 30 music keys
Here is a table with all the minor and major keys. You can also see these keys using the Circle of Fifths.
|Major Key||Relative Minor||Sharps/Flats|
|Cb||Ab||Bb, Eb, Ab, Db, Gb, Cb, Fb|
|Gb||Eb||Bb, Eb, Ab, Db, Gb, Cb|
|Db||Bb||Bb, Eb, Ab, Db, Gb|
|Ab||F||Bb, Eb, Ab, Db|
|Eb||C||Bb, Eb, Ab|
|A||F#||F#, C#, G#|
|E||C#||F#, C#, G#, D#|
|B||G#||F#, C#, G#, D#, A#|
|F#||D#||F#, C#, G#, D#, A#, E#|
|C#||A#||F#, C#, G#, D#, A#, E#, B#|
You don't have to know all these keys.There are certain keys that work best on guitar. Start with them.
Wait! What is Cb? Is not the same of B?
Cb and B have the same pitches, but they are called with a different name because of the enharmonics.
Interesting fact about sharps and flats in the table above
By looking at the keys table above, we can derive an interesting insight:
If we take two keys, with the second one semitone below the first, the sum of sharps in the first key and the flats in the second key is always 7
- A major has 3 sharps. Ab major has 4 flats: 3 + 4 = 7
- G major has 1 sharps. Gb major has 6 flats: 1 + 6 = 7
- Eb major has 3 flats. E major has 4 sharps: 3 + 4 = 7
- F# major has 6 sharps. F major has 1 flat: 6 + 1 = 7
- C major has 0 sharps. Cb has 7 flats: 0 + 7 = 7
Why keys are only major and minors? What about the other modes?
As the minor key is built on the 6th degree of a major key, we could be tempted to include keys built on the other degrees: Mixolydian on the 5th degree, Lydian on the 4th, and all the other modes.
Actually, major and minor keys have a unique characteristic not present in any other mode: tritone resolution.
In the key of C, there's a tritone interval between B and F (6 half-steps, the most dissonant interval)
This interval is in the dominant chord built on the 5th degree (G7, that is G B D F)
The resolution of the tritone B F to C E (one note, B, goes up to C, and F goes down to E) can only happen to Cmaj or Amin, then they are the strongest tonal centers, more important than the other modes.
In other words, they feel home better.
Play this sequence (B F to C E) on your guitar to really understand what I mean.
This is an interesting discussion on Reddit about the superior tonal center class of major and minor keys.
How Many Keys Exist? Conclusions
I'll leave you with a cool video in which Victor Wooten, the legendary bass player, explains this stuff:
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