Final answer:
In Mendelssohn's Hebrides Overture, the strings section introduces the first subject. This reflects the advancements in instrument craftsmanship during the 19th century, particularly impacting the expressivity and complexity of orchestral music from the Romantic era.
Step-by-step explanation:
The first subject of Mendelssohn's Hebrides Overture, also known as Fingal's Cave, is introduced by the strings section of the orchestra. The flowing melody that is characteristic of this piece is first played by violins and cellos, setting a contemplative mood that mimics the rolling waves of the sea near the Hebrides archipelago off the coast of Scotland. Mendelssohn's orchestration in this overture showcases the technical advancements of musical instruments during the 19th century, such as the improvement in mechanical valves and keys for the woodwind and brass instruments, which enabled them to produce a bigger, fuller, and better-tuned sound. These innovations allowed for greater expressivity and more intricate compositions, as seen in the Romantic era's rich orchestral music.