The Charles de Mestral Papers are the personal items of Charles de Mestral (1944 - ), 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 Correspondence series contains cards and letters to or from Donald Mackey. The series is arranged chronologically by time period as indicated. The series includes correspondence of special note to/from Rev. David R. L. Clarke, Prime Minister of Canada Pierre-Elliot Trudeau, Alfred Whitehead and Healy Willan.

Sonde Papers consist of correspondence, documentation, audio and video pertaining to activities of Sonde (formerly named MUD, Musical Design).