Over several years, Bertrand Denzler and Jean-Luc Guionnet have interviewed approximately 50 musicians from various backgrounds about their practice of musical improvisation. Musicians include both the very experienced such as Sophie Agnel, Burkhard Beins, John Butcher, Rhodri Davies, Bill Dixon, Phil Durrant, Axel Doerner, Annette Krebs, Daunik Lazro, Mattin, Seijiro Murayama, Andrea Neumann, Jerome Noetinger, Evan Parker, Eddie Prevost and Taku Unami, as well as those newer to the field. Asked questions on topics such as the mental processes behind a collective improvisation, the importance of the human factor in improvisation, the strategies used and the way musical decisions are made, the interviewees highlight the habits and customs of a practice, as experienced by those who invent it on a daily basis. The interviews were carefully edited in order to produce a sort of grand discussion that draws an incomplete map of the blurred territory of contemporary improvised music.