liminfoKey Signature Reference
Free web tool: Key Signature Reference
Key
C major
Relative Minor
A minor
Accidentals
None
Accidental Notes
None
Scale Degrees
C
I (Tonic)
D
II (Supertonic)
E
III (Mediant)
F
IV (Subdominant)
G
V (Dominant)
A
VI (Submediant)
B
VII (Leading)
Circle of Fifths
About Key Signature Reference
The Key Signature Reference is a free, interactive music theory tool that covers all 13 major keys — from C major (no accidentals) through the sharp keys up to F# major (6 sharps) and the flat keys down to Gb major (6 flats). For each selected key, the tool instantly displays the key name, its relative minor, the number and specific accidentals (sharps or flats), and all seven scale degrees with their Roman numeral function labels: I (Tonic), II (Supertonic), III (Mediant), IV (Subdominant), V (Dominant), VI (Submediant), and VII (Leading Tone).
Music students, composers, guitarists, pianists, and music teachers use this reference to quickly check which notes are sharp or flat in a given key, which diatonic chords belong to a key, and how keys relate to each other around the Circle of Fifths. The interactive SVG Circle of Fifths diagram highlights the currently selected key and shows all 12 positions with their relative minor labels, making the visual relationship between adjacent keys immediately apparent.
Technically, the tool pre-computes all key data as static JavaScript objects and uses a single dropdown selector to switch between keys. The Circle of Fifths is rendered as an inline SVG with trigonometrically positioned circles at 30-degree intervals. No server requests, no external libraries beyond React, and no user data is collected. The tool works instantly on any device without any loading delay.
Key Features
- All 13 major keys: C, G, D, A, E, B, F# (sharp keys) and F, Bb, Eb, Ab, Db, Gb (flat keys)
- Per-key display: key name, relative minor, accidental count, and specific sharp/flat note names
- Seven scale degree cards with Roman numeral labels (I Tonic through VII Leading Tone)
- Tonic (I) highlighted in blue for immediate identification of the home note
- Interactive SVG Circle of Fifths diagram with the selected key highlighted
- Relative minor labels displayed inside the Circle of Fifths at each position
- Dropdown selector showing accidental count for each key for quick orientation
- Fully client-side — instant key switching with no server requests
Frequently Asked Questions
How many sharps or flats does each major key have?
C major has none. Moving clockwise: G has 1 sharp (F#), D has 2 (F#, C#), A has 3, E has 4, B has 5, F# has 6. Moving counter-clockwise: F has 1 flat (Bb), Bb has 2, Eb has 3, Ab has 4, Db has 5, Gb has 6. Each step around the Circle of Fifths adds one accidental.
What is the relative minor of each major key?
Every major key has a relative minor that shares the same key signature (same notes). To find it, count down a minor third (3 semitones) from the tonic, or go to the 6th scale degree. Examples: C major → A minor, G major → E minor, F major → D minor, Bb major → G minor. They share identical sharps and flats.
What are the seven scale degrees in a major key?
The seven scale degrees are: I (Tonic) — the home note; II (Supertonic) — one step above; III (Mediant) — midway between I and V; IV (Subdominant) — one step below V; V (Dominant) — the most harmonically tense degree; VI (Submediant) — same as the relative minor root; VII (Leading Tone) — one semitone below the octave, creates tension resolving to I.
What is the Circle of Fifths?
The Circle of Fifths is a visual arrangement of all 12 major keys in a circle, where each adjacent key is a perfect fifth (7 semitones) apart. Moving clockwise adds one sharp; moving counter-clockwise adds one flat. The Circle of Fifths is an essential tool for understanding key relationships, chord progressions, and modulation between keys.
Why do F# major and Gb major have the same notes?
F# major and Gb major are enharmonically equivalent — they use the same pitches but spelled differently. F# major uses 6 sharps (including E#, which sounds like F), while Gb major uses 6 flats (including Cb, which sounds like B). In equal temperament tuning they are identical in sound; the choice between them depends on musical context and readability.
How do I use key signatures when reading sheet music?
Key signatures appear at the beginning of each staff after the clef, showing which notes are always sharp or flat throughout the piece. For example, the key of D major shows F# and C# on the staff, meaning every F and C in the piece should be played sharp unless a natural sign cancels it. This eliminates the need for individual accidentals on every note.
What chords naturally occur in each major key?
Each major key has seven diatonic chords built on its scale degrees: I and IV and V are major chords; II, III, and VI are minor chords; VII is a diminished chord. For example, in C major: C major (I), D minor (II), E minor (III), F major (IV), G major (V), A minor (VI), B diminished (VII). The V chord (dominant) is the most important for creating harmonic tension that resolves to I.
How does this tool help with music composition or songwriting?
When composing or writing songs, knowing the key signature tells you which chords and notes naturally fit together without causing dissonance. You can use this reference to find the diatonic chords of your key, understand which chords create tension (V, VII) versus resolution (I, IV), and identify closely related keys for modulation by checking adjacent positions on the Circle of Fifths.