The tonalities of the fugues follow the order of his Serie 1 and use the keynote C (see The Craft of Musical Composition).
[citation needed] Ludus Tonalis can be thought of as the most direct application of Hindemith's theory that the twelve tones of the equally tempered scale all relate to a single one of them (called a tonic or keynote).
The affinity of each note with the keynote is directly related to its position on the harmonic scale.
The first performance of Ludus Tonalis in Italy was played by Eunice Katunda in 1948 at the Teatro Piccolo in Milan.
Ludus Tonalis consists of 25 movements:[4] There is a striking symmetry around the center of the cycle (the march).