Tonic (music)

In music, "tonic" refers to the originating note or chord of a particular key.

Scales are based on their tonic pitch, or tonic note, which is why they begin and end with their tonic pitch. This is also why scales are named after their tonics: for instance, the tonic of the C major scale is the note C. In the movable do solfège system, the tonic note is sung as do.

"Tonic" may also refer to the tonic triad, which is a triad built on the tonic pitch, or more generally to a tonic chord of another quality. The tonic often functions as the tonal center or final resolution tone of tonal music, and is commonly the goal of the final cadence in tonal harmony.

In very much conventionally tonal music, harmonic analysis will reveal a broad prevalence of the primary (often triadic) harmonies: tonic, dominant, and subdominant (i.e., I and its chief auxiliaries a 5th removed), and especially the first two of these.

The tonic is distinguished from the root, which is the note on which a chord is built. While the tonic pitch serves as the root of a tonic chord, it is not the root of other chords.

In Roman numeral analysis, the tonic triad is typically symbolized by the Roman numeral "I" if it is major and by "i" if it is minor. While tonic triads are most prevalent, tonic chords may also appear as seventh chords: in major, as IM7, or in minor as i7 or rarely iM7:

Importance and function

In music of the common practice period, 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 scale degree above the tonic, or the fourth below it) in between.