The Ensemble «mit vier» is an "affair of the heart" of Kaspar. Not only because his sister and two of his best friends are involved, but also because it is the oldest ensemble in which Kaspar has been taking part.
The ensemble was founded in 1992 on the occasion of the final exams of Charlotte and Kaspar Zehnder. The program included Mozart's quartet in C major, which is still today one of the standard works for this instrumentation. In the meantime, «mit vier», whose name, by the way, derives from the game of Skat, which the members of the ensemble cultivated on tours, significantly expanded its repertoire. Alongside with Mozart the classical and romantic quartets by Antonín Reicha, Ferdinand Ries, Franz Krommer, Paul Wranitzky, Caspar Kummer, Ferdinand Thieriot, Bernard Henrik Crusell, Luigi Boccherini or Joseph Haydn are an integral part of the concert programs. The ensemble has continuously performed also newer quartets, trios and duos e.g. by Virgilio Mortari, Arthur Honegger, Frank Martin, Albert Roussel, Gottfried von Einem, Edison Denisow or Ferdinand Weiss, as well as the works by Swiss composers Armin Schibler, Volkmar Andreae, Jean-Luc Darbellay, Giorgio Tedde, Hans Eugen Frischknecht, Fritz Voegelin.
Gabrielle Brunner, Katrin Frauchiger, Katharina Weber and Marco Antonio Perez Ramirez are currently writing new pieces for the Ensemble «mit vier». They will be premiered in spring 2015 in the context of "l'Art pour l'Aar".