Although I never had any 'official' lessons with him, Heinz Holliger has become and will always remain a lifelong teacher to me. And we have developed a friendship that started 10 years ago, in Davos, where he heard me playing Robert Schumann's Fantasiestücke Op. 73 for the first time. Since then, we have performed together countless times, stood on (and behind) the stage, discussed, philosophized…