Check out this legally free ebook:

  • A Manual of Gregorian chant compiled from the Solesmes books and from ancient manuscripts (Rome, Tournai (Belgium): Society of Saint John the Evangelist/Desclee, Lefebvre & Co., Publishers to the Holy See and Printers to the Sacred Congregation of Rites, 1903). With Imprimatur. Also with approbation from Pope Leo XIII addressed to Abbot Paul Delatte, O. S. B., of Solesmes. Available at Internet Archive and Open Library (which reports: “Includes the Ordinary of the Mass in Latin with an English paraphrase by Dom Gueranger, and a commentary in English on the religious service.”)

For more legally free ebooks, visit the Catholic eBooks Project.