The bass-baritone Klaus Mertens was born in Kleve, in the Lower Rhine, and embarked on his singing career, performing in Germany and abroad, as soon as his training was completed. Since then he has established himself as a noted performer in Baroque oratorio, collaborating with distinguished conductors, particularly in the works of JS Bach. In October 2003 he finished the complete recording of Bach Cantatas with the Amsterdam Baroque Orchestra under Ton Koopman, a project that had taken ten years, with concomitant tours in Europe, America and Japan, marking the high point of his career. At the same time he has won a reputation as a Lieder singer, in repertoire ranging from the origin of the form to the contemporary. He has a particular interest in the rediscovery, promotion and revival of hitherto unknown repertoire. He regularly appears with well-known orchestras and conductors and at international festivals, and has participated in the recording of 155 CDs and DVDs and made numerous broadcasts and television appearances.