circle of fifths / relative major-minor pairs
... F major - D minor C major - A minor G major - E minor D major - B minor A major - F#/Gb minor E major - C#/Db minor B major - G#/Ab minor F#/Gb major - D#/Eb minor C#/Db major - A#/Bb minor G#/Ab major - F minor D#/Eb major - C minor A#/Bb major - G minor F major - D minor C major - A minor ...