This study examines a source which has been often neglected by historians up until now: songs from the oral tradition. It considers how this documentation can be used in order to renew our knowledge of Breton society between the sixteenth and the eighteenth centuries. Breton songs must be analysed by comparing them constantly to written and iconographic archives, which usually form the basis of historical research. The comparison with judicial archives is particularly relevant and has been strongly developed. This methodological approach is completed by an application of conclusions in a large field of research including material culture, social and political behaviour, mobility of people and ideas and religious attitudes. This study lies at the intersection of several scientific heritages : it is first and foremost linked to a historical approach, but it is opened to other disciplines such as ethnology.