It is now broadly accepted that Vaughan Williams's music betrays a more complex relation to national influences than has traditionally been assumed. It is argued in this thesis that despite the trends towards revisionism that have characterized recent work, Vaughan Williams's interest in and engagement with English folk materials and cultures remains only partially understood. Offering contextual interpretation of materials newly available in the field, my work takes as its point of departure the critical neglect surrounding Vaughan Williams's contradictory compositional debut, in which he denounced the value of folk song in English art music in an article published alongside his song 'Linden Lea', subtitled 'A Dorset Folk Song'. Reconstructing the under-documented years of the composer's early career, it is demonstrated that Vaughan Williams's subsequent 'conversion' and lifelong attachment to folk song emerged as part of a broader concern with the intelligible and participatory quality of song and its performance by the human voice. As such, it is argued that the ways in which this composer theorized an idea of 'song' illuminate a powerful perspective from which to re-consider the propositions of his project for a national music. Locating Vaughan Williams's writings within contemporaneous cultural ideas and practices surrounding 'song', 'voice', and 'Englishness', this work brings such contexts into dialogue with readings of various of the composer's works, composed both before and after the First World War. It is demonstrated in this way that the rehabilitation of Vaughan Williams's music and reputation profitably proceeds by reconstructing a complex dialogue between his writings; between various cultural ideas and practices of English music; between the reception of his works by contemporaneous critics; and crucially, by considering the propositions of his music as explored through analysis. Ultimately, this thesis contends that Vaughan Williams's music often betrays a complex and self-conscious performance of cultural ideas of national identity, negotiating an optimistic or otherwise ambivalent relationship to an English musical tradition that is constructed and referenced through a particular idea of song.