Key

Reading the key

The key signature at the start of the line gives away the key. How a key signature differs from accidentals within the bar, and in which order the flats appear, is explained on the page Accidental; the order of the sharps is under Sharp. Both orders are steps of a fifth, and that is exactly what the circle of fifths makes visible.

Two rules shorten the reading: in sharp keys the tonic lies a semitone above the last sharp. In flat keys the tonic is the second-to-last flat; with only one flat the key is F major.

Major or minor?

The key signature alone does not answer the question, because every key signature belongs to two keys: a major key and its relative key in minor. Two clues decide:

• The ending: If the melody ends on the tonic and the last chord is a major triad, the piece is in major. If it is a minor triad, it is in minor.
• Accidentals: In minor the raised seventh degree appears as an accidental. In A minor that is a G♯.

Why keys exist

In every key the degrees have fixed jobs: the first is the tonic, home, and the fifth the dominant, which pulls back to the tonic. A key is therefore more than a list of notes. It creates tension and resolution. Playing the same song in another key is called transposing: all notes move by the same distance, and the degrees stay the same.

Common mistakes

• No sharps or flats, so C major: A minor also has no sharps or flats. The ending settles the key.
• Spelling: Write the note letter as a capital and the mode in lowercase: “G major”, “E minor”.