"It is a far cry from the date of the first extant opera to the music-dramas of Richard Wagner. The opera, as regards its essential form, is old enough. [T]he Greeks knew it, and it was probably well established before their time. In the tragedies of Aeschylus, Sophocles, and Euripides, there was musical recitation, and the choruses were sung in unison. But only a measure or two of this ancient music remains to show what it was like. It is to the age of the Renaissance, with its attempts to revive old-time Greek art, that we owe the first specimens of what we mow understand as opera."