Berlin clubbers know Sollmann from turning knobs behind the decks of Berghain and co. as DJ Efdemin. For his latest project, he put away his electronic gadgets to focus on the microtonal theories of US composer Harry Partch as well as replicas of artist Harry Bertoia's sound sculptures. And if that wasn't enough, he dug up a 150-year-old double siren designed by German physicist Hermann von Helmholtz. Don't worry, you don't have to be a theory geek to enjoy the world premiere of Monophonie at Volksbühne on Feb 7. Sollmann talked us through the basics.