Final answer:
The vocal style that mimics speech and is accompanied by basso continuo in operas, specifically opera buffa like those of Rossini, is known as recitative. It is influenced by the commedia dell'arte tradition and serves to advance the plot through spoken dialogue.
Step-by-step explanation:
The vocal style you are referring to is known as recitative, which is designed to imitate the natural rhythms and inflections of speech. In recitative, the singer is accompanied only by a basso continuo, advancing the plot through a dialogue or monologue. This style is prominent in opera, particularly the opera buffa (comic opera) of composers like Rossini. The focus on speech-like rhythm makes it distinct from more melodic and structured arias. Remarkably, this style was influenced by earlier theatrical traditions, such as the commedia dell'arte, which heavily featured stock characters and improvisational dialogue, and laid the foundation for stylized stage performances that integrated dramatic storytelling with music.