Fonds consists of private correspondence related to Clarke’s professional work, a few musical manuscripts and texts of addresses, and a large body of personal financial accounts. His correspondence falls into two series. The general correspondence discusses arrangements for concerts in England and Canada, compositions (his own and others), the problems of musical life in Montréal, and private matters such as travel arrangements and club memberships. Much of the correspondence concerns the social aspects of music and of Clarke's position: patronage of musical events, organization of celebrations for the Jubilee of 1935 and the Coronation in 1937, and complementary tickets to concerts. Amongst his correspondents are a number of musicians and composers, including Sir Ernest MacMillan and Healey Willan. A very small percentage of this material concerns university business. A second series consists of invitations to address or attend meetings, with related correspondence. Both series cover the years 1929-1952.

Over half of the papers consist of personal financial accounts (1929-1953) for Clarke's insurance, taxes, apartment rental, various domestic expenses (e.g. groceries), telegrams, travel, and transportation.

There are two undated addresses: one on Christmas and the second on musical education. There are also two music sketchbooks from around 1920. Pictorial material comprises two photographs (approximately 1923, 1954) and a pencil sketch (1933).