The Sonde Collection provides a thirty-five year span of documentation for a Montreal-based Canadian experimental musical group who were very active electroacoustic composers and performers in the 70s and 80s. Sonde (formerly named MUD, Musical Design), created and played sound sources in Quebec, Canada and Europe. Sonde’s compositions were generally conceived for live performance on original sound sculptures. Using meditative improvisation, the group produced new music with sounds created by electroacoustic amplification and transformation.
The Sonde Collection is divided into 26 series and contains approximately 1,900 items. The majority of the collection consists of correspondence, concert posters and programs, and audio and video recordings. Activities of the Sonde group are described together as Sonde Papers and the activities of Charles de Mestral, a founding member of the group as Charles de Mestral Papers.
In the Sonde Papers, whenever it has been possible to do so, each item is referenced to the events listing, a numbered, chronological listing of events created by the group, entitled: ACTIVITES DU GROUPE SONDE (1975-2010) / Sonde Activities (1975-2010). The Sonde Papers include posters, programmes, scores, photographs, audio and video recordings.
The Charles de Mestral Papers are the personal items of Charles de Mestral, a member of the Sonde group from its inception. Whenever it has been possible to do so, each item is referenced to the events listing entitled: RÉALISATIONS DANS LE DOMAINE DE L’INSTALLATION SONORE (1985-2013, Charles de Mestral) / Sound Installations (1985-2013, Charles de Mestral) a numbered, chronological list of activities of Charles de Mestral. The Charles de Mestral Papers include scores, correspondence, installation plans, clippings, audio recordings and publications.

Collection consists of programs related to an appearance by Harry Belafonte in Montreal in support of the Society to Overcome Pollution's environmental aims. Also contains a clipping, manuscript notes, and a typescript signed Mona Elaine Adilman about Quebec environmental legislation.

The Sir William Osler Collection, distinct from the Bibliotheca, is an extensive archival holding of Osler's correspondence (including eighteen hundred original letters), daybooks, accounts, engagement books, legal documents, book invoices, membership certificates, notebooks, lectures, addresses, newspaper clippings, photographs, books with manuscript additions, and miscellaneous loose items formerly inserted into individual books in his library. The collection also contains various family papers, including correspondence of Lady Grace Revere Osler and Edward Revere Osler.

The collection consists of a selection of records reflecting Sir Arthur Currie's tenure as Principal of McGill University from 1920 to 1933. His administration was marked by the establishment of the Faculty of Music, the School for Graduate Nurses, and the Faculty of Graduate Studies and Research. Constructed during this period were Moyse Hall, the Roddick Gates, a Biology Building (now the F. Cyril James Administration Building), and additions to Royal Victoria College and Redpath Library. Currie died in office on 30 November 1933. His records form a part of the McGill University's executive and administrative records, RG2: Office of the Principal and Vice-Chancellor. The Principal is the academic head and chief administrative officer of the University. Under the original Charter of 1821, the Principal constituted with the Board of Governors and the Fellows (now the Senate) a body politic and corporate. Later amendments to the Charter and changes in the University statutes have not significantly altered the position of Principal. Ex officio, by virtue of his office, the Principal is also Vice-Chancellor of the University, a member of the Board of Governors and Chairman of the Senate. Frequently, it has been the Principal's vision and personality which have determined the course of McGill's development; therefore, the records not only document the administrative activities of the office, but also often reflect the character of the whole institution. Currie's records fall more or less into the three general series: external correspondence, internal administration and academic matters.

There is business correspondence, 1792-1800, with letters from among others Alexander Mackenzie, Joseph Frobisher, Alexander Henry, Simon Fraser and Roderick Mackenzie. There are also minutes and resolutions of the Executors of McTavish in a bound volume; and a contemporary copy of the minutes of the executors of his will, 1805.

Collection consists of 59 heraldic plaques featuring Royal Navy and Royal Canadian Navy badges for ships and naval installations.

This collection consists of letters written by Canadian soldiers serving in the Second World War, between 1943 and 1944. The letters were written to family members or romantic partners, while the soldiers were in training in England, or deployed in Europe. The collection also includes some letters written to the soldiers. Contents of the letters chiefly concern news from home and the daily life of soldiers.

The collection is divided into three series, one for each soldier. Series 1 contains correspondence between Robert C. Parsons and his wife, Peggy Parsons. Series 2 contains correspondence between Jack Mills and his mother, C.I. Mills, and brother, Bob Mills. Series 3 contains correspondence between A.V. "Mac" Cormack and his girlfriend Florence Morgan Graham, as well as a letter from Mac's roommate G.D. "Jerry" Royds, also to Florence.

The collection consists of programs and recordings of ensemble performances (including opera) by students, faculty members, and guest artists associated with the Schulich School of Music at McGill University and performed at one of the School's halls (Pollack Hall, Redpath Hall, Tanna Schulich Hall, and Clara Lichtenstein Hall), as well as some performances at venues outside McGill.

The collection consists of reports and plans for urban and rural areas from all provinces of Canada and some international cities, including Boston, New York, Chicago, France, and London, dating from the late 1950s to the 1990s. Most of the material consists of plans and reports for future land-uses that are revised, usually every decade. It also includes regulations for these areas, such as zoning. Some reports deal with sectorial policies such as housing, transportation, conservation, or environmental protection.

The collection consists of 38 letters written by a small group of French Canadian Protestant friends living in the villages of St. Philippe, Grande Ligne, and Ste. Philomène in southern Quebec, as well as in the city of Montreal. Among the letters are those by Samuel Perrier, a Quebec farmer and dedicated letter writer, primarily addressed to his future wife, Eugenie Molleur (1862–1948), and to one of his daughters, Aline, who attended L'Institut Méthodiste Français.

These letters provide a vivid depiction of the challenging rural life faced by Quebec farmers, highlighting issues such as fatigue, poor crop yields, a shortage of farm labour, harsh winters, health struggles, and local news. They also reflect the parents' determination to improve their children's futures by sending them to school to learn English, accounting, music, and teaching. The collection additionally includes a small selection of poems and songs.