Born in Bern, Demenga studied with Walter Grimmer, Antonio Janigro, Leonard Rose and Mstislav Rostropovich and at the Juilliard School in New York, among others.
He gives concerts as a chamber musician and soloist at all important festivals and music centres of the world.
An extensive series of CD recordings, published by ECM, documents his artistic work.
In 2002, the last CD of his recording of Bach's solo suites in combination with works by contemporary composers Heinz Holliger, Elliott Carter, Sándor Veress, Bernd Alois Zimmermann, Isang Yun and Toshio Hosokawa was released.
Demenga has worked with conductors like Moshe Atzmon, Myung-Whun Chung, Charles Dutoit, Claus Peter Flor, Howard Griffiths, Heinz Holliger, Armin Jordan, Okko Kamu, Rostropovich, Dennis Russell Davies, Wolfgang Sawallisch, Sándor Végh, Mario Venzago and Hiroshi Wakasugi.