Answer · Theory
What key is my song in, and which chords fit it?
A song's key is the note and scale its melody and chords come to rest on. Find the chord that sounds like home, usually the one the chorus or the last bar lands on, then check the notes used against that major or minor scale. The chords that fit are the seven built on the notes of that scale.
Finding the key
Play the song and stop it at a point of rest, such as the end of a chorus. The note you want to hum there is the tonic, and the chord under it names the key. Then check the other notes: a song in C major uses C D E F G A B, and a note outside that set is either a passing colour or a sign the key is something else.
Every major key shares its notes with a minor key three semitones below it. C major and A minor use the same seven notes. What separates them is which chord feels like home: if the song keeps settling on Am, it is in A minor.
The chords that belong to a key
Build a triad on each note of the scale and you get the key's own chords.
| Degree | In a major key | C major | In a minor key | A minor |
|---|---|---|---|---|
| 1 | I, major | C | i, minor | Am |
| 2 | ii, minor | Dm | ii°, diminished | Bdim |
| 3 | iii, minor | Em | III, major | C |
| 4 | IV, major | F | iv, minor | Dm |
| 5 | V, major | G | v, minor (often played major) | Em or E |
| 6 | vi, minor | Am | VI, major | F |
| 7 | vii°, diminished | Bdim | VII, major | G |
In a major key, I, IV, V and vi carry most popular songs. In a minor key, i, VI, III and VII do the same job, and the fifth chord is often played major (E in A minor) because its raised third pulls harder back to the tonic.
Chords from outside the key
A chord from outside the scale is not wrong. The common ones are borrowed from the parallel key (F minor or B♭ in a song in C major) or are dominant chords aimed at a chord other than the tonic (D7 leading to G). They work because they resolve to a chord that does belong.
In Zammoth
The transport's KEY cell shows the key and mode detected from your audio. The engineer reads that key, and it can also detect the chords in a recording and tell you how confident each reading is. Ask it directly:
In the piano roll, the SCALE switch highlights the song's key on the keyboard and snaps the notes you draw or drag to it, so a MIDI part stays inside the chords above. See the manual on song intelligence.
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