What a Key Signature Tells You
At the start of a piece (after the clef and before the time signature), a key signature shows a group of sharps or flats. Every note of that letter name is played sharp or flat throughout the piece unless marked otherwise.
- Sharps (♯) raise a note by a half step
- Flats (♭) lower a note by a half step
- Key signatures apply to all octaves of the affected note
- A key signature corresponds to one major key and one relative minor key
Sharp Keys
Sharps are always added in a fixed order: F – C – G – D – A – E – B. To find a sharp key's name, go up a half step from the last sharp.
| Sharps | Key | Sharps Present | Relative Minor |
|---|---|---|---|
| 0 | C Major | — | A minor |
| 1 | G Major | F♯ | E minor |
| 2 | D Major | F♯ C♯ | B minor |
| 3 | A Major | F♯ C♯ G♯ | F♯ minor |
| 4 | E Major | F♯ C♯ G♯ D♯ | C♯ minor |
Flat Keys
Flats are always added in a fixed order: B – E – A – D – G – C – F. To find a flat key's name, look at the second-to-last flat.
| Flats | Key | Flats Present | Relative Minor |
|---|---|---|---|
| 1 | F Major | B♭ | D minor |
| 2 | B♭ Major | B♭ E♭ | G minor |
| 3 | E♭ Major | B♭ E♭ A♭ | C minor |
| 4 | A♭ Major | B♭ E♭ A♭ D♭ | F minor |
Major and Minor Keys
Every key signature corresponds to two keys: a major key and its relative minor (sharing the same key signature).
| Concept | Definition | Example |
|---|---|---|
| Relative Minor | Minor key sharing the same key signature; starts a minor 3rd below the major | C Major → A minor |
| Parallel Minor | Minor key with the same starting note but a different key signature | C Major → C minor (3 flats) |
| Circle of Fifths | Each key is a perfect fifth apart; sharps increase clockwise, flats counterclockwise | G (1♯) → D (2♯) → A (3♯) |
Quick check: For sharp keys, the last sharp is always a half step below the tonic. For flat keys (except F), the second-to-last flat is the tonic.