Composers’ libraries, as collections of texts, have undergone few investigations, hence leading to a lack of recognition of their intellectual and hermeneutic values in musicology. However, since the 19th century, because of the development of musicology and the appropriation of musical criticism by musicians, the composer is no longer just a craftsman but a thinker of his art: he becomes an intellectual. An examination of the library of Vincent d’Indy (1851–1931) and his writings altogether, makes it possible to clarify an intellectual dynamic peculiar to this composer, and more precisely to reveal the primordial epic dimension of the library, which is thus at the origin of a cross-referenced reflection on the literary epic and what d’Indy calls “the musical epic”.