How do brass instruments primarily differ from woodwinds?

Brass instruments are characterized by their unique method of sound production, which involves the player's buzzing lips creating vibrations. The correct answer highlights that brass instruments possess a cup-shaped mouthpiece and are constructed from metal tubing. This design is integral to their sound; the shape of the mouthpiece and the tubing influences pitch and tone quality. The metal allows for a bright, clear sound that is distinctive to brass instruments, such as trumpets, trombones, and tubas.

The other options do not accurately represent the fundamental differences between brass and woodwind instruments. For example, woodwinds typically use reeds to create sound, which is a significant distinction from how brass instruments operate. Additionally, while some brass instruments can be quite large, size is not a definitive factor that separates the two families, as there are also large woodwind instruments. Lastly, asserting that brass instruments do not use air for sound production is incorrect, as air flow is essential for the sound to be produced in both brass and woodwind instruments. Thus, the emphasis on the cup-shaped mouthpiece and metal tubing underscores the key distinction in construction and sound production methods between these two categories of instruments.