In studies of the relationship between relaxation and music, that between brain waves and chords has often been reported despite the fact that “harmony” rather than single chords is listened for in most cases. This raises the problem of whether brain waves measured in subjects differ when harmony is listened to from when single chords are listened to. As a first step toward solving this problem, we propose original experiments in presentation sound, analytical object, and time zone, clarifying that brain waves were influenced by both chords and of chord correlation in harmony.