Keys & Transposition

If you move a song to another key, is it still the same song? Move the melody below with your own hands and you will have the answer.

Press play and listen to this little melody living in C major. Then get to work: delete each note and re-add it two rows higher (each row is a semitone, so two rows is two semitones) until the whole thing lands in D major — C becomes D, E becomes F♯, G becomes A, and so on. Play it again and compare.

What a key is

A piece of music usually lives inside one major scale, and that scale is its key. Saying a song is in G major means its notes mostly come from the G major scale, and home is G. The melody may wander off to visit, but it usually comes home at the end.

The key signature: sharps on the doorplate

Each key uses a fixed set of sharps or flats, so notation simply lists them once at the start of every line — that is the key signature. C major has none; G major has one sharp (F♯); F major has one flat (B♭). One glance at the key signature tells you which key the music lives in.

Transposition: moving house, keeping the shape

Moving every note by the same interval is called transposition. Since the distances between notes — the shape of the melody — never change, it still sounds like the very same tune, only higher or lower as a whole. When a singer finds the original key too high, the band drops the entire song two semitones: same song, more comfortable house.

Take this with you

• A key is the major scale the music lives in; the tonic is home.
• The key signature lists that key's fixed sharps or flats at the start of the staff.
• Transposition moves everything by the same interval: the shape stays, the home changes.