The music is not everything in opera. Its full enjoyment can be achieved only with the knowledge of the words that are being sung -- usually in a foreign language. In this series, the librettos are presented in the original language with an English line by line translation. This, it is possible to follow the song and to understand the meaning of the foreign words. The selection of the operas to be included in this volume was determined largely by importance and popularity as indicated by the number of performances at the Metropolitan Opera House in the past 56 years. - Foreword.