Johannes Keller, harpsichordist and specialist in rare meantone music with more than the usual twelve tones per octave, comes to Amsterdam from Basel by invitation of the Huygens-Fokker Foundation to give a unique concert. Here he will perform both the 31-tone organ and his own ‘chromatic-enharmonic’ harpsichord. The programme features several composers, such as Georg Muffat, Ascanio Mayone, and Nicola Vicentino, who in the 16th and 17th centuries attempted to expand meantone tuning so that modulations to previously unreachable keys became possible. The use of these ‘new’ tones occasionally resulted in experiments producing unusual harmonic transitions. A highlight of this concert is that the renowned German composer and cellist Caspar Johannes Walter will compose a new work for violin and 31-tone organ. Johannes Keller will be musically accompanied in several works by violinist Eva Saladin.