The key of C major can be played on a piano entirely on the white keys, needing no sharps or flats. What minor key can be played using the same all-white keys, with no sharps or flats?

The reason A minor can be played using only the white keys on a piano is due to its special relationship with the key of C major. In music theory, these two keys are known as relative keys. This means they share the exact same notes and the same key signature, which in this case is no sharps and no flats. The C major scale is built from the notes C, D, E, F, G, A, and B. The natural minor scale of A contains the very same notes, just starting and ending on A: A, B, C, D, E, F, G.

This shared collection of notes is why both scales can be played without touching any of the black keys. The primary difference between C major and A minor lies in their tonic, or starting note. This change in the tonal center is what gives each key its distinct emotional character. While C major is generally perceived as bright and happy, A minor has a more somber or melancholic sound, a common characteristic of minor keys.

The concept of relative keys is a fundamental part of Western music. Every major key has a relative minor, and its starting note is always found three semitones below the starting note of the major key. For instance, the relative minor of G major (which has one sharp) is E minor, and the relative minor of F major (which has one flat) is D minor. This interconnectedness allows for smooth transitions between major and minor moods within a piece of music.