The Prélude proceeds by juxtaposition of 7 harmonic variations alternating the cantus of C H A R B E L (consisting of the French correspondence between letters and notes), between left hand and right hand, with gradation of nuances from pianissimo to fortissimo. The subject of the Fugue derives from an ornamentation of the cantus of the Prélude and gives rise to a contrapuntal and tonal development modulating throughout the cycle of fifths.