Final answer:
Mendelssohn uses rapid staccato passages and descending arpeggios in the flutes to emulate the sound of raindrops in his compositions, creating a vivid auditory representation of rainfall.
Step-by-step explanation:
Mendelssohn portrays raindrops in the flutes during his pieces primarily through rapid staccato passages and descending arpeggios. This musical technique effectively simulates the pitter-patter of rain as it strikes various surfaces, similar to how raindrops might dance rapidly on the pavement. The rapid, short, detached notes of the staccato create the sensation of raindrops hitting the ground, while the descending arpeggios mirror the manner in which rain falls from the sky to the earth, often perceived as coming down in a kind of cascade. Such musical elements work together to craft an auditory representation of rainfall.