Sobre el océano is a critical edition and a complete voice and piano reduction of a Mexican Zarzuela by Antonio de Maria y Campos, a XIX-century composer virtually unknown until today. As with all books in the collection, this volume provides a bilingual -Spanish-English- introductory study contextualizing the work and the composer. It also provides translations into English of the libretto and phonetic (IPA) transcriptions.The Spanish Zarzuela, a form of light opera with spoken dialogue interspersed with musical numbers and sung lyrics, was the most popular musical genre in the second decade of the 19th century in cities such as Madrid, Mexico City, Havana, and Buenos Aires. Unlike the opera, which was established as the spectacle of the elites, the Zarzuela had a greater impact on the popular classes by describing regional uses and customs of urban and rural Spain and, later, the traditions of the new American nations. To recover Sobre el océano, a work written in 1897 by Antonio de María y Campos and Manuel Larrañaga Portugal, just at the height of Zarzuela in Mexico, allows to understand Mexican history and culture of the late nineteenth century and offers singers the opportunity to interpret a genre of great beauty for the enjoyment of audiences around the world. This score is a gem to be discovered.