Whilst scholars often rely on a close reading of the score to understand English musical style at the turn of the fifteenth century, a study of the compositional techniques composers were taught provides complementary evidence of how and why specific stylistic traits came to dominate this repertory. This essay examines the relationship between practical and theoretical sources in late medieval England, demonstrating a link between the writings of two Oxford-educated musicians, John Tucke and John Dygon, and the polyphonic repertory of the Eton Choirbook (Eton College Library, MS 178), compiled c. 1500–4. Select case studies from this manuscript suggest that compositional and notational solutions adopted at the turn of the fifteenth century, having to do particularly with metrical proportions, echo music-theoretical concepts elucidated by Tucke and Dygon. These findings impinge upon the current debate concerning the presence of a network between educational institutions in the south-east of England during this period.