Cavalieri was a major figure in the early Baroque, producing several of the cantatas and pastorales that led the way to Baroque-style oratorio and opera, as well as intermedi, ancestors of the intermezzo and of opera in general. His La rappresentazione di Anima e di Corpo is claimed by some music scholars as the first oratorio, by others as the first opera. Most of his works are lost, but contemporary writings and commentaries suggest that he might also have written the first recitative.
Unlike many composers, he was born into the aristocracy, and held various positions for the Rome branch of the de' Medici family, as well as that of organist for the Oratorio del Santissimo Crocifisso. When Ferdinando de' Medici became Grand Duke of Tuscany in 1587, Cavalieri went with him to Florence where he superintended the court's artistic employees, including artists and musicians, and was a sort of stage manager and producer for plays and dances, as well as Inspector General of Arts and Artists. Florence was home to the Camerata Fiorentina, of which Peri, Corsi, Marco da Gagliano, Giulio and his daughter Francesca Caccini, and Vincenzo Galilei were members, and is arguably the city where opera and oratorio were born. The first major performances of his works were in 1589, when Ferdinando married Christine of Lorraine, and among the entertainments were the play La Pellegrina, for which Cavalieri wrote intermedi (musical interludes somewhere between incidental music and intermezzos), including the Ballo del Gran Duca, for which many later composers wrote variations and improvisations. During the succeeding year, for further court entertainments, he wrote various pastorales and solo cantatas, none of which survive. However, since much of the music of his Florentine contemporaries survives, we do have a sense of what they might have been like.
In 1600, his La rappresentazione di Anima e di Corpo was first performed at the Oratorio della Vallicella in Rome. While often described as an oratorio, it was drawn from the old morality plays, and Cavalieri left specific instructions for its dramatic presentation as well as recommendations for the orchestration, choreography, and for the vocal ornamentation. It was originally performed as a three-act work with two intermezzos between each act. While he returned to Florence to supervise and participate in the entertainments celebrating the wedding of Maria de' Medici and Henry IV of France, he soon returned to Rome. His health and eyesight were both failing, and he died there shortly afterwards.