To find the key of a song, look at the key signature first, then find the chord the song ends on, which is usually the tonic, and check which scale the melody uses. If the song ends on C and has no sharps or flats, it is in C major or A minor, and the final chord tells you which one.
How do you find the key of a song?
Finding the key of a song means working out which scale and which tonic chord the music is built around, and there are three clues to use: the key signature, the final chord, and the melody. The key signature tells you the sharps or flats, which narrows the key down to two possibilities, a major and its relative minor. The final chord is usually the tonic, so if the song ends on C major, it is probably in C major, and if it ends on A minor, it is probably in A minor. The melody confirms it: if the melody uses the notes of the C major scale and keeps returning to C, the key is C major. The process is detective work, not guesswork, and it gets easier with practice. Start with the key signature, which gives you two candidates. Then look at the first and last chords, which are usually the tonic. Then look at the accidentals, the sharps and flats written in the music itself: if a piece with no sharps or flats has a G# in the melody, it is probably in A minor, because the G# is the raised 7th of the harmonic minor scale. Then check the chords: if the V chord is major, the key is probably minor, because minor keys use a major V chord from the harmonic minor scale. The key finder finds the key from a set of chords, and the chord to key finder finds it from a chord progression.
How the clues fit together
The key signature is the first clue, because it tells you the sharps or flats. A piece with one sharp, F#, is in G major or E minor. A piece with two flats, Bb and Eb, is in Bb major or G minor. A piece with no sharps or flats is in C major or A minor. That narrows the key down to two, and the other clues decide between them. The final chord is the strongest clue, because most pieces end on the tonic: if the last chord is G major, the key is G major, and if the last chord is E minor, the key is E minor. The accidentals are the next clue, because they reveal the harmonic minor scale. If a piece in one sharp has a D# in the melody, it is probably in E minor, because D# is the raised 7th of E harmonic minor, and the V chord, B major, needs the D#. If a piece with no sharps or flats has a G#, it is probably in A minor, because G# is the raised 7th of A harmonic minor. The chords confirm it: if the V chord is major, the key is minor, and if the V chord is minor, the key is probably major. The key of E minor shows the chords of a minor key, and the key of G major shows the chords of its relative major.
Worked example — a song with two sharps. The key signature has F# and C#, so the key is D major or B minor. The song ends on a B minor chord, so the key is probably B minor. The melody contains an A#, which is the raised 7th of B harmonic minor, and the V chord is F# major, which confirms it: F# major needs the A#, and the V chord of a minor key is major. The key is B minor, and the key of B minor lists its chords: Bm, C#dim, D, Em, F#m, G and A, with F# major as the V chord from the harmonic minor scale.
How to practise finding keys
Practise by working out the key of music you already know, starting with the key signature and the final chord, and checking your answer against the chords.
- Pick a song you know, find its key signature, and work out the two possible keys before you look at the chords.
- Look at the first and last chords of the song, and decide whether the key is major or minor from the final chord.
- Look for accidentals in the melody, especially raised 7ths, and use them to confirm a minor key.
- Play the chords of the key of C major and the key of A minor, and practise telling them apart by ear.
- Use the key finder to check your answer, and repeat the exercise with a different song each day.
Common mistakes
- Trusting the key signature alone — A key signature with one sharp could be G major or E minor, because they share the signature. The key signature narrows the key down to two, but it cannot tell you which one it is on its own.
- Ignoring the final chord — Most pieces end on the tonic chord, so the final chord is the strongest clue to the key. If you ignore it, you are throwing away the best evidence you have.
- Forgetting the harmonic minor scale — A raised 7th in the melody is the signature of a minor key, because it comes from the harmonic minor scale. If you see a G# in a piece with no sharps or flats, the key is A minor, not C major.
Quick reference
This table lists the four clues for finding the key of a song, in the order you should use them, with what each clue tells you and what to look for. The key signature narrows the key down to two, the final chord picks one of them, the accidentals confirm a minor key, and the chords confirm the whole answer.
| Clue | What to look for | What it tells you |
|---|---|---|
| Key signature | Sharps or flats at the start | Two possible keys: major or relative minor |
| Final chord | The last chord of the song | Usually the tonic, so it names the key |
| Accidentals | Raised 7th in the melody | Confirms a minor key (harmonic minor) |
| Chords | Major V chord | Confirms a minor key (harmonic minor) |
Practise the table by working out the key of a song you know, using the clues in order, and writing down your answer at each step before you move to the next clue. When you can work out the key of any song in under a minute, you have the skill, and you will never need to guess again.
Frequently asked questions
How do I find the key of a song?
Look at the key signature first, then find the chord the song ends on, which is usually the tonic, and check which scale the melody uses. If the song ends on C and has no sharps or flats, it is in C major or A minor, and the final chord tells you which one.
What is the easiest way to tell major from minor?
Look at the final chord: if it is major, the key is probably major, and if it is minor, the key is probably minor. Then look for a raised 7th in the melody, which confirms a minor key, because it comes from the harmonic minor scale.
Can a song change key?
Yes, and many do. A song can modulate to a closely related key, such as the dominant or the relative minor, and the key signature may change, or the modulation may use accidentals instead. Look for a new tonic chord and a new set of accidentals to spot the change.
What if a song has no key signature?
Then it is in C major or A minor, or it is using accidentals instead of a key signature. Look at the final chord and the melody to decide which one, and look for a raised 7th to confirm a minor key.
Can I use a tool to find the key?
Yes. The key finder works out the key from a set of chords, and the chord to key finder works out the key from a chord progression. Both tools use the circle of fifths and the diatonic chords to narrow down the possibilities.