Tonicize

Tonicize is a term in music theory describing the temporary treatment of a pitch class or chord as if it were the tonic, creating a momentary shift of tonal center within a larger key. This technique provides a sense of direction or color without establishing a permanent key change.

Tonicization is usually achieved through the use of secondary dominants, leading-tone chords, or other chromatic or diatonic chords that imply a new center. The characteristic feature is a local emphasis on the target chord or scale degree, often reinforced by cadences that resolve toward that center, followed by a return to the original key.

Tonicization differs from modulation in that it is local and transient. A modulation involves a real change of key center and, typically, a new key signature or a longer-lasting reinterpretation of the tonal center. Tonicizations produce momentary possibilities without committing the entire piece to a new key.

Common examples include a progression in C major that uses D7 (the V of V) resolving to G major (the V) and then returning to C. Other approaches use secondary dominants to various degrees (such as V/vi leading to vi), or create a temporary ii–V–I within the imagined key. In practice, tonicization can occur across classical, jazz, and popular styles, varying in duration and functional emphasis.