In 2001, he turned to installation as his artistic form and public space as his performance site (transition 2001, Ortsklang Marl Mitte German Sound Art Award 2002).
With the Swiss performance artist Steffi Weismann he created dialogical, interactive installations (pickup 2005, takeaway 2006, venture doll 2008, UNorJUSTNESS A+B 2013).
In 2009, Sprich mit mir in the red-light district of Braunschweig and RamallahTours in Israel were realized, the latter dealing with a fake in public space and the internet.
In 2020, he received the Audio Walk Award for his soundwalk toposonie::engelbecken, which connects historical radio testimonies with the present in a place steeped in history.
Klein's work investigates sites and situations, focusing on their inherent contradictions, which he transforms aesthetically to serve as a topic for discussion and deliberation.
Through his site-specific installations, concert works, and audio-based sound walks, he invites the public’s perception of the border between art and reality to be challenged and explores trans-border, audio-visual communication spaces.
Techniques for this include the use of artistic fabrication, which guides the recipient into an uncertain terrain to question identities and encourages critical reflection.
While these themes are more widespread in new media art, one finds no other artists in that field who have given the musical and the auditory the same precedence, nor is there the same kind of connection to place that Klein has developed.