From the earliest days of musicology, the definition of the so-called ‘simple’ polyphonies, thein geography and position in the general historical development of polyphony, have been matters of dispute. This article aims particularly to describe how and why the geographical extent of the repertory of simple polyphony has always been a contentious subject. After giving a brief historiographical overview of the different geographical definitions, the author especially focuses on the polyphonic mini-corpus of the diocese of Lausanne in Switzerland as a case study proposing a new approach, which attempts to better include the ‘simple’ polyphonies, regionally and through the course of time.