The Companion to the Sarum Rite contains explanations, elucidations, and supplements that provide a fuller understanding of the material. Its content is organized by reference to the page numbers of the Latin Edition.
Text sources are indicated wherever possible. The Breviary-Psalter itself uses the Vulgate (Gallican) text. However, Antiphons, Responsories, Versicles, and Mass Propers are drawn not only from the Gallican Psalter but also from the Vetus Romana (Old Roman) Psalter. In many cases the texts of both sources are identical, but where the text is drawn specifically from the Gallican or Old Roman Psalter, this is indicated. In a few cases the chant-text in fact takes elements from both.