Tonic (music)

In music, the tonic is the first scale degree of a diatonic scale and the tonal center or final resolution tone. The triad formed on the tonic note, the tonic chord, is thus the most significant chord. More generally, the tonic is the pitch upon which all other pitches of a piece are hierarchically referenced. Scales are named after their tonics, thus the tonic of the scale of C is the note C. Simple songs may begin and end on the tonic note.

The tonic is often confused with the root, which is the reference note of a chord, rather than that of the scale. It is also represented with the Roman numeral I.

Importance and function

In western European tonal music of the 18th and 19th centuries, the tonic center was the most important of all the different tone centers which a composer used in a piece of music, with most pieces beginning and ending on the tonic, usually modulating to the dominant (the fifth above the tonic, or the fourth note down from the tonic) in between.

Two parallel keys have the same tonic. For example, in both C major and C minor, the tonic is C. However, relative keys (two different scales that share a key signature) have different tonics. For example, C major and A minor share a key signature that feature no sharps or flats, despite having different tonic pitches (C and A, respectively).