Minor scales have their own key signatures, just like major scales. They're based on the natural minor scale, which shares a key signature with its relative major. This makes it easy to remember and write out.

The harmonic and melodic minor scales use the same key signature as the natural minor. Any raised notes in these scales are shown with accidentals, not in the key signature. This keeps things simple while allowing for different minor scale variations.

Key signatures of minor scales

Natural, harmonic, and melodic minor key signatures

• The key signature for a natural minor scale has the same sharps or flats as its relative major key, which is a minor third above the tonic of the minor key
• The key signature for a harmonic minor scale is the same as the key signature for the natural minor scale
  • The raised 7th scale degree in the harmonic minor scale is not included in the key signature and instead is notated with an accidental (G# in A harmonic minor)
• The key signature for a melodic minor scale is the same as the key signature for the natural minor scale when the scale is descending
  • When ascending, the melodic minor scale raises both the 6th and 7th scale degrees (F# and G# in A melodic minor ascending), which are not included in the key signature and instead are notated with accidentals
• The key signatures for minor scales can contain up to 7 flats (E♭ minor) or 7 sharps (D# minor), with C minor and A minor having zero flats or sharps in their key signatures

Examples of minor key signatures

• D minor has one flat (B♭) in its key signature, which is the same as its relative major key of F major
• G minor has two flats (B♭ and E♭) in its key signature, which is the same as its relative major key of B♭ major
• E minor has one sharp (F#) in its key signature, which is the same as its relative major key of G major
• B minor has two sharps (F# and C#) in its key signature, which is the same as its relative major key of D major

Constructing minor key signatures

Using the circle of fifths

• The circle of fifths can be used to determine the key signature for any minor key by counting clockwise from C minor for sharp keys or counterclockwise from C minor for flat keys
• Each step clockwise around the circle of fifths adds one sharp to the key signature, with the new sharp being added on the 7th scale degree of the new key
  • For example, moving clockwise from A minor (no sharps or flats) to E minor adds one sharp (F#), and moving clockwise again to B minor adds another sharp (C#)
• Each step counterclockwise around the circle of fifths adds one flat to the key signature, with the new flat being added on the 4th scale degree of the new key
  • For example, moving counterclockwise from D minor (one flat, B♭) to G minor adds another flat (E♭), and moving counterclockwise again to C minor removes the flat, resulting in no flats or sharps

Order of sharps and flats in key signatures

• The order of sharps in a key signature is always F#, C#, G#, D#, A#, E#, B#
  • This can be remembered using the mnemonic "Father Charles Goes Down And Ends Battle"
• The order of flats is always B♭, E♭, A♭, D♭, G♭, C♭, F♭
  • This can be remembered using the mnemonic "Battle Ends And Down Goes Charles' Father"

Identifying minor keys

Determining the minor key from a key signature

• To determine the minor key from a given key signature, first identify the relative major key by going down a minor third from the last sharp in the key signature (for sharp keys) or going up a major second from the second-to-last flat (for flat keys)
  • For example, if the key signature has three sharps (F#, C#, and G#), the last sharp is G#, and going down a minor third from G# leads to E, so the relative major key is E major, and the minor key is C# minor
  • If the key signature has four flats (B♭, E♭, A♭, and D♭), the second-to-last flat is A♭, and going up a major second from A♭ leads to B♭, so the relative major key is B♭ major, and the minor key is G minor
• Once the relative major key is identified, the minor key will share the same tonic as the relative major key
• If there are no sharps or flats in the key signature, the minor key is A minor

Examples of identifying minor keys from key signatures

• Key signature with two sharps (F# and C#): relative major key is D major, minor key is B minor
• Key signature with three flats (B♭, E♭, and A♭): relative major key is E♭ major, minor key is C minor
• Key signature with one sharp (F#): relative major key is G major, minor key is E minor
• Key signature with no sharps or flats: minor key is A minor

Relative major vs minor key signatures

Shared key signatures and pitches

• Relative major and minor keys share the same key signature, as they contain the same pitches
• The relative major key is always a minor third above the tonic of the relative minor key
  • For example, the relative major key of A minor is C major, which is a minor third above A
• Conversely, the relative minor key is always a major sixth below the tonic of the relative major key
  • For example, the relative minor key of F major is D minor, which is a major sixth below F

Examples of relative major and minor key pairs

• C major and A minor (no sharps or flats)
• G major and E minor (one sharp, F#)
• F major and D minor (one flat, B♭)
• D major and B minor (two sharps, F# and C#)
• B♭ major and G minor (two flats, B♭ and E♭)

Differences between relative major and minor keys

• While relative major and minor keys share the same key signature, they differ in their tonic, scale degrees, and overall tonality
• The tonic of the relative major key functions as the mediant (3rd scale degree) in the relative minor key
  • For example, in the key of A minor, the tonic is A, while in its relative major key of C major, C functions as the mediant in A minor
• The scale degrees in a minor key are different from those in its relative major key due to the lowered 3rd, 6th, and 7th scale degrees in the natural minor scale
  • For example, in A minor, the scale degrees are A (tonic), B (supertonic), C (mediant), D (subdominant), E (dominant), F (submediant), and G (subtonic), while in its relative major key of C major, the scale degrees are C (tonic), D (supertonic), E (mediant), F (subdominant), G (dominant), A (submediant), and B (leading tone)