This was soon followed by a busy concert career both at home and abroad. Klaus Mertens has worked with renowned “early music” specialists such as Ton Koopman, Frans Brüggen, Nicholas McGegan, Philippe Herreweghe, René Jacobs, Sigiswald Kuijken, Gustav Leonhardt, Nikolaus Harnoncourt; as well as great conductors of the classical repertoire such as Gary Bertini, Herbert Blomstedt, Enoch zu Guttenberg, Peter Schreier, Kent Nagano, Hans Vonk, Christian Zaharias, Edo de Waart, Kenneth Montgomery, Gerard Schwarz, Ivan Fischer and many others.
In addition he has very successfully worked with famous orchestras over the world, such as Amsterdam Baroque Orchestra, Concertgebouw-Orchester Amsterdam, Jerusalem Symphony Orchestra, the great orchestras in Berlin, Gewandhaus-Orchester Leipzig, Dresdner Philharmonie, Saint Louis Symphony Orchestra, Chicago Symphony Orchestra, Tokyo Metropolitan Symphony Orchestra and so on.
Klaus Mertens is also a regular guest at numerous international festivals such as the Mozart Festival Lille, Bach-Tage Berlin, Flanders Festival, Prague Spring, Schleswig-Holstein Festival, Handel Festival Oxford, Bach Festival Los Angeles, Ancient Music Festival Utrecht, Festival Liturgica Jerusalem, Bologna Festival Musica, Maggio Musicale Florence, European Music Festival Stuttgart, Klangbogen Festival Vienna, Salzburg Festival, Festival d’Aix-en-Provence, Festival de Beaune, Festival d’Ambronay, Lucerne Festival, Mostly Mozart Festival New York, BBC Proms, etc.
Klaus Mertens is known to be one of the most prominent and sought-after interpreter of the baroque oratorio and concert repertoire, and he has repeatedly recorded the great vocal works of J.S. Bach with many different conductors. The recording of the complete cantatas of Bach with the Amsterdam Baroque Orchestra initiated by the conductor Ton Koopman has been finished in October 2003. Tilman Michael of the magazine fono forum remarked about his singing in the series that “...I don’t know any other bass but Klaus Mertens who is such an eminent interpreter of Bach.” The entire project, which took 10 years to complete and included concert tours throughout Europe, America, and Japan marked a significant highlight in his singing carrier; Klaus Mertens is the first and the only singer to have sung all of Bach’s vocal works for a complete CD recording series and also in concerts.
Klaus Mertens also devotes himself equally successfully to singing Lieder from early to modern times. His concert repertoire covers a great range from Monteverdi to contemporary composers, including some that were especially written for him.
A discography of more than 120 CDs along with many international radio and television broadcasts testify to Klaus Mertens’ competence as a celebrated, versatile singer.
