At this book's core is a critical edition of letters exchanged over 50 years between Anglo-Irish composer Elizabeth Maconchy (1907-1994) and the Welsh composer Grace Williams (1906-1977). These two innovative and talented women are highly regarded for their music, their professional activities, and their roles in British musical life. The edition comprises around 353 letters from 1927 to 1977, none of which have been published before, along with scholarly introductions and contextualisation. Interwoven commentaries, in tandem with carefully constructed appendices, frame the letter texts. Moreover, the commentaries and introductory essays highlight and track the development of important themes and issues that characterise the study of twentieth-century British music today. This edition presents a dialogue, through both sides of a unique correspondence, offering an alternative commentary on musical and cultural developments of this period.