What is the term for the Italian instrumental pieces of tender, lyrical character that emerged in the 18th century?

The term that best describes the Italian instrumental pieces characterized by their tender and lyrical qualities that emerged in the 18th century is "Romance." This genre often features expressive melodies and is typically associated with the emotional and personal expression found in instrumental music of that period.

Romances were designed to evoke sentimentality and a sense of intimacy, often conveying deep feelings through their melodic lines and harmonic progressions. This genre reflects the broader trends of the time, which included a focus on emotion and individual expression, distinguishing it from more structured forms like the symphony or serenade, which embrace different stylistic features and functions in the musical repertoire.

In contrast, while a serenade may also possess a lyrical quality, it traditionally refers to music written for outdoor performance, typically meant for entertainment. A symphony represents a more grandiose orchestral form characterized by complexity and variety, and a ballade typically refers to a narrative or story-like structure expressed in music, which does not align with the characteristics of the tender and lyrical pieces described.