How can two keys that share the same seven pitches produce different emotional characters?
Think about your answer, then reveal below.
Model answer: The emotional character of a key is determined not by which pitches are present but by which pitch functions as the tonal center — the point of resolution and 'home.' When A is treated as the gravitational center among the shared pitches, the ear hears minor-mode patterns. When C is treated as home, the ear hears major-mode patterns. Tonality is about hierarchy and function among pitches, not just pitch content.
This is the deeper insight behind relative keys. The tonic pitch organizes all other pitches around it — some act as leading tones that pull toward home, others as stable resting points. Shifting the tonal center rewrites those functional relationships even when the pitches do not change. A composer can modulate between C major and A minor using identical harmonies, simply by placing cadences on different notes and emphasizing different resolutions.