MusicReasonScales, Keys, Intervals, and Notation
What's adjacent to this key on the circle of fifths?
Choose a major key. This tool shows its signature, its relative minor, and its immediate neighbors one fifth in each direction, without claiming that visual proximity alone makes for a good modulation.
Answer
Want to learn more? Keys, Modulation, and Harmonic Direction
Understand
Adjacent keys on the circle share all but one accidental, which is exactly why they are common modulation destinations, but sharing a signature relationship is not the same as being the right destination for a specific piece. The circle organizes key relationships; it does not evaluate whether a particular modulation will sound good in context.
Worked example
Moving clockwise from C major lands on G major, one additional sharp. Moving counterclockwise from C major instead lands on F major, one flat, confirming the two directions are genuine inverses of each other.
Method and limitations
Each key's position is its fifths count from C (positive for sharp keys, negative for flat keys); moving clockwise adds one fifth, counterclockwise subtracts one. This launch version covers major keys only, showing the relative minor alongside each position rather than a separate minor-key circle.
Why fifths, specifically
The circle is built on fifths rather than any other interval because a perfect fifth is the smallest step that changes exactly one accidental at a time: moving by a fifth adds or removes a single sharp or flat, which is what makes the circle's geometry line up so cleanly with key-signature counts. Arranging keys by any other interval would not produce this same one-accidental-per-step property.