At the end of the last century, a team of researchers has formed in the Midwest – a musical movement quickly dubbed “post-rock” which, once will not hurt, borrowed some of the jazz ideals. This trend was first led by Tortoise, who found its ease among everything likely to be used like samba, dub, ambient, minimalist music, concrete or industrial, krautrock, free, etc.. Until 2010 when the city of Chicago offers to celebrate the diversity of music produced in their environment with a new suite and several guests from the worlds of jazz and improvisation. For Sons d’hiver, and several French improvisers, Tortoise tries again to cross the worlds by going through a panel of music mirrors.