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.

The Hellmuth Wolff Organ Collection consists primarily of organ plans, pamphlets, photographs, books and periodicals, and personal correspondence. The majority of these documents are associated with or represent one of the fifty organs in Wolff’s opus. In addition to depicting Wolff’s instruments, the collection of organ plans also includes Wolff’s drawings for proposed but not-constructed organs, plans by other organ builders, and plans drawn by Wolff that are based on historical models and treatises by writers such as Dom Bédos. Of the photographs, most are associated with specific Wolff organ projects and represent a span date of the late 1960s to the early 2000s. Also in the photograph collection are images of historical organs in Europe, which Wolff presumably used in modelling and designing several of his instruments, as well as images associated with other organ projects by builders such as Casavant Frères, Karl Wilhelm, and Rieger, all of whom Wolff worked with before establishing his own workshop in Laval. The collection of pamphlets includes programs, program notes, and concert series information for several of the Recitals and concerts performed on Wolff’s instruments. Of the periodicals and books, titles include The American Organist, Choir & Organ, and Orgelforum. Also in the collection are several three-dimensional models, or maquettes, of Wolff organs.