What technique involves the artistic elaboration of a subject in music?

The technique that involves the artistic elaboration of a subject in music is known as development. In musical composition, development refers to the process where the initial musical idea or theme is transformed and expanded upon. This can include variations in melody, harmony, rhythm, and dynamics, along with the introduction of contrasting material.

During the development section of a piece, composers take the original subject and manipulate it—sometimes by altering its pitch, changing its rhythmic values, or presenting it in a different key—to create musical interest and complexity. This practice is essential in Western classical music, especially within forms like sonata form, where development plays a critical role in the overall structure of the piece.

In contrast, improvisation refers to spontaneously creating music without prior preparation, which does not necessarily elaborate on a pre-existing subject. Composition is the act of creating a complete piece of music but doesn't specifically focus on the elaboration of themes. Notation pertains to the system of writing music down, which is a separate skill from the artistic development of musical ideas. Thus, development is the correct answer as it directly relates to the elaboration and transformation of musical subjects.