Guide · Guitar theory
How to find the key of a song
To find the key of a song, list its chords and look for the key that contains them all; the chord the song keeps coming back to, often the first and the last, is the key's home chord. If that home chord is minor, the song is in the The major and minor keys that share all seven notes and the same key signature, such as C major and A minor. of the major key you found.
List the chords
Write down every chord in the song once, ignoring repeats and the order they come in.
Say a song uses G, D, Em and C. Four chords is plenty to go on. A chord sheet, a tab or your own ears all work; even the bass notes alone are often enough.
Leave out anything that looks unusual for now, such as a single chord that appears once in a bridge. Most songs stay inside one key for most of their length, and the odd chord is easier to explain once you know the key.
Find the key that holds them all
Compare the chords with the seven chords of each key; usually only one major key contains them all.
G, D, Em and C all belong to G major, whose chords are G, Am, Bm, C, D, Em and F♯°. No other major key has all four: C major has C, G and Em but its D chord is minor, and D major has G and D but no C.
A quick shortcut: look for the major chords. In a major key there are only three, I, IV and V, and they sit side by side on the circle of fifths. Find three neighbouring major chords among the song's chords and the middle one is usually I.
The chart of every key makes this a quick scan: find the row that contains every chord you wrote down.
Listen for home
The key's home chord is the one that sounds finished: songs tend to start there and nearly always end there.
A major key and its The major and minor keys that share all seven notes and the same key signature, such as C major and A minor. share their chords, so the list alone cannot tell G major from E minor. Your ear can. Play the song and stop on each chord in turn: the one where the music feels at rest is home.
A song that goes Em, C, G and D and keeps returning to Em is in E minor, even though every one of those chords is also in G major. E minor has one sharp: F♯.
When a chord does not fit
One chord outside the key is normal; the most common ones are the major V in a minor key and chords borrowed from the The major and minor keys that share a tonic but not all their notes, such as C major and C minor..
In minor keys the V chord is often made major so it pulls harder towards home. In A minor, the natural v chord is Em, but most songs play E or E7 instead. Its G♯ is the raised seventh of the The natural minor scale with its 7th raised a half step, which makes the V chord major and gives it a strong pull home. scale, and it does not change the key.
Major-key songs often borrow from the parallel minor: a ♭VII or a minor iv. F in a song in G, or Cm in a song in G, are both borrowed. They add colour without moving the key.
If several chords stop fitting at once and a new chord starts to sound like home, the song has changed key. That is a Changing key within a piece of music, so a different note becomes home., and it often happens for a final chorus.
Use the key signature or the melody
With sheet music, the The sharps or flats written at the start of each line of music, telling you which notes the key changes. narrows it down to a major key and its The major and minor keys that share all seven notes and the same key signature, such as C major and A minor.; without it, the melody's notes do the same job.
One sharp means G major or E minor; two flats means B♭ major or G minor. The key signatures guide shows how to read any signature in seconds, and each key's page shows its signature on the staff.
Without notation, pick out the melody on one string and write down the notes it uses. Seven different notes that fit one major scale point to that key or its relative minor, and the note the melody ends on is usually the home note.