What does "chromaticism" refer to in music theory?

Chromaticism in music theory refers to the incorporation of notes that are outside the traditional diatonic scale, which consists of the seven notes that define a particular key. This inclusion expands the harmonic and melodic vocabulary of a piece, creating richer textures and emotional depth.

By using chromatic notes, composers can add tension, color, and complexity to their music, moving beyond the constraints of the specific scale tied to a key. This practice is common in many musical styles, particularly in Romantic and 20th-century music, where composers often sought to explore new expressive possibilities.

In contrast, the other choices focus on more restrictive aspects of music—whether adhering strictly to a scale, emphasizing a certain musical element like melody, or following notation precisely—all of which do not encompass the broader implications of using chromaticism to enhance musical expression.