This Italian composer bridged the 16th and 17th centuries—the eras of madrigal songs and opera arias. He wrote nine books of the former, leaving his mark with harmonic ingenuity, and more than a dozen operas, only three of which survive. The horns that introduce 1607's L'Orfeo reveal the form's original purpose: pomp in celebration of the Gonzaga court. By 1642, opera was a popular medium, with sensuality taking center stage, as Monteverdi's L'incoronazione di Poppea demonstrates. (Courtly types also started to come in for some mockery.) Listen and discover the roots of classical song.