What is a musical instrument primarily used for?

A musical instrument is specifically designed to generate melodic sounds, which is its primary function. Instruments such as pianos, guitars, violins, and drums have mechanisms that allow them to produce music through vibrating strings, air columns, or membranes. This production of sound can encompass various musical styles and genres, making instruments essential for creating melodies, harmonies, and rhythms that contribute to musical pieces.

While some other options might involve artistic expression or creativity, they do not pertain directly to the fundamental purpose of a musical instrument. For example, producing visual art refers to activities such as painting or sculpting, which rely on different skills and techniques. Performing athletic routines is associated with physical activities and sports practices, and creating written compositions relates to the format of writing, which is distinct from producing musical sounds. Ultimately, the essence of musical instruments lies in their ability to create music, underscoring the correctness of selecting the option related to generating melodic sounds.