In music, the key is the pitch of the tonic of the musical scale used. Tonal music gravitates toward a home key, the tonic. Key is established by the use of a fixed scale of notes based on this tonic note and can be emphasized by other, related notes and by cadences. The tonic note or chord assumes greater importance than the others and leads, by extension, to a hierarchy of chords with the dominant (based on the fifth note of the scale) of particular significance.
See temperament.