How To Figure Out The Key to A Song

How Can You Know What The Key Is To A Song.

First off: what does “key” mean? How do you define the musical term “key”?
For an explanation of this, check this blog: The Difference Between Key and Scale.

Now we got that covered: let’s move on to a listing of ways you can figure out the key to a song.

The first chord
Songs almost always start with the first chord of the scale the song is written with.
If a song is in the key of G, the first chord is almost always a G chord. If the song is in F# minor, the first chord usually is an F#m chord.
The last chord
Songs almost always end with the first chord of the scale the song is written with.
Usually, when a song is in the key of C, the song ends on a C chord.
The key signature.
When you are learning a song from a book or chart, the key signature at the beginning of the staff tells you what scale the song is written with.
Of course, this requires some theoretical knowledge about key signatures.
A key signature is a number of sharps or flats that are notated at the beginning of a piece of music, right next to the clef.
That number of sharps or flats “signifies” the key/scale because there is only one specific major scale that has that x number of #s or b’s.
(The major scale is the most commonly used scale in our music that all our music theory is based on),
The Chord progression.
The chords in a progression are derived from a scale.
Chords are just notes of a scale that you group together into a chord shape.
You then hit all these notes in that chord shape all simultaneously.
If you know what the notes are of each individual chord in a chord progression, then you can from there on figure out what the scale is that these chords are built from.
For example, in the following chord progression:
F | G | C | C ||
The notes in an F chord are: F A C
The notes in a G chord are: G B D
The notes in a C chord are: C E G
I get the notes C D E F G A B (all the white keys of the piano)
All the white keys of the piano = a C major scale.
This chord progression is in the key of C major.
You could also of course memorize how the chords are organized in a major scale.
Imajor IIminor IIIminor IVmajor Vmajor VIminor VIIdim
Translating this to for example a C major scale, that gives:
C Dm Em F G Am Bdim
Looking at this from a different angle, you see:
1. 2 major chords in a song, that are a whole step apart, then these 2 chords are IV and V in the key (granted that the song is in a major key)
2. 2 minor chords a whole step apart, those chords are are always II- and III- in the (major) key
3. A dim triad is always VII in the key.
Examples:
If I see an F#dim chord, I know that song is in the key of G. (F# is the 7th note in the key of G)
If I see G followed by an A chord in a song, then that song is in the key of D
(G and A are the 4th and 5th chord in the key of D major. It’s as simple as counting alphabet: DEFGA = 12345)
The notes in your vocal melody.
When you are writing a song and you have a melody that comes to you, figure out on your guitar what the notes are that you just sang.
Then based on that info, figure out what the scale is.
This requires 2 things:
i. An ear that is good enough to be able to figure out the notes you sang on guitar.
ii. Enough theory knowledge about key signatures to figure out what the scale is that the notes in your melody add up to.
The key (center).
Every song has a key center: a “gravitational” note that supports the whole song and which the whole song is centered around.
It is that one note you can sing throughout the whole song and it never clashes anywhere (unless of course, the song modulates to a different key during the song).
It requires some good ear to hear that key center note.
It is very often the first note in the song the bass player plays (and the very last note he plays).
It is also very often the root of the very first chord in the song since most songs typically start with the I chord.

Conclusion

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