After his studies as a classical singer Matthias Rettner performed mainly as a concert singer in the 1990s. He then began to apply his efforts to increasingly cross-genre projects which could no longer be assigned to any traditional category and joined the Action Theatre PAN.OPTIKUM in 1999. It is based in Freiburg and artistically led by Sigrun Fritsch with a focus on performances in public venues.

He has been working with Berlin-based concept artist and designer Peter Zizka since 2003. With PAN.OPTIKUM and Zizka his objectives are mainly artistic international cooperation projects with a social relevance.