Scales, Keys & Modes

Key

Definition

A key is the tonal home of a piece of music: a central note, the tonic, plus the scale and chords built around it. A piece in G major treats G as home and uses mostly the notes of the G major scale.

When musicians say a piece is "in G major", they are naming its key. The key tells you two things at once: which note is home (the tonic, here G) and which kind of scale the music mostly draws on (here the major scale, with its F♯). Melodies tend to end on the tonic, chords lean toward the tonic chord, and the other notes of the scale take their roles around it.

Major keys and minor keys

A key is either major or minor. A major key uses the major scale on its tonic; a minor key uses the minor scale, usually mixing its natural, harmonic and melodic forms. With twelve possible tonics and two kinds of key, there are 24 keys. Three major keys and three minor keys can each be spelled two ways (F♯ major and G♭ major, for example), so you will see 30 key names in all, but those enharmonic equivalent pairs sound the same on a piano.

Key and key signature

The key signature at the start of each staff shows the sharps or flats the key needs, so you do not have to write them in front of every note. G major has one sharp, F♯; F major has one flat, B♭. But each key signature belongs to two keys: one sharp means G major or E minor, its relative minor. To tell which:

Look at the last note of the melody and the last chord. Most pieces end on the tonic.
Look for an extra accidental. Minor keys usually raise their 7th degree, so a D♯ in a one-sharp piece points to E minor.

Two treble-clef examples in 4/4 with a one-sharp key signature. First: quarter notes G A B G, C B A F-sharp, then a whole-note G. Second: E F-sharp G E, A G F-sharp D-sharp with a printed sharp, then a whole-note E. — The same key signature, one sharp, in two keys. The first tune centers on G, leans on F♯ and ends on G: G major. The second centers on E, raises D to D♯ (its leading tone) and ends on E: E minor.

How to find the key of a song

The same steps work by ear. Hum the note that feels like the resting point at the end of a phrase: that is probably the tonic. Then ask whether the music sounds major or minor. The chords help too: a song whose chords are mostly G, C, D and Em is very likely in G major.

The G major scale uses one black key, F♯ (coral). That is why the key signature of G major has one sharp.

Keys and the circle of fifths

Keys are related to one another in a regular way. Moving the tonic up a perfect fifth adds one sharp (C, G, D, A...), and moving it down a fifth adds one flat (C, F, B♭, E♭...). The circle of fifths lays them all out like a clock, and keys next to each other there share six of their seven notes. That closeness is why music most often modulates to a neighboring key.

Other meanings

"Key" also names a lever on an instrument: the keys of a piano, or the keys a flute player presses. And in everyday speech, "changing the key" of a song usually means transposing it: moving the whole thing higher or lower, for example to suit a singer.

Name the Key Signatures and Write the key signatures build the reading skill, and Key Signatures: Major & Minor is a chart of all fifteen.

Common questions

How many keys are there in music?

Twenty-four: a major and a minor key on each of the twelve notes. Because some keys can be spelled two ways (F♯ major and G♭ major, for example), there are 30 key names and 15 key signatures.

What is the difference between a key and a key signature?

The key is the tonal home of the music: its tonic and its scale. The key signature is the group of sharps or flats written at the start of the staff to show that scale. One key signature is shared by two keys, a major key and its relative minor.