Final answer:
The "brassy" timbre of brass instruments is affected by the metal construction, the flared bell, and the player's lip vibrations on the mouthpiece. All of these elements work together to give brass instruments their unique sound.
Step-by-step explanation:
The "brassy" timbre of brass instruments is influenced by several factors. The factors which contribute to a brass instrument's distinctive sound include A) the metal construction of the instrument, B) the flared bell at the end of the instrument, and C) the vibration of the player's lips on the mouthpiece. The metal construction allows for clear sound projection and contributes to the instrument's bright, resonant quality. The flared bell aids in the spreading of sound waves, affecting the instrument's overall timbre. The lip vibrations, or embouchure, directly impact the instrument's pitch, volume, and quality of sound.