Old Roman chant occupies a central position. It provides the key to the musical filiation between Jerusalem and the Greek heritage, while also enabling us to understand the treasures of Koranic cantillation. The mystery of the incarnation of the Word irrigates the chants presented here. Through the magic of music, sung texts become icons. The Word is deployed with a sovereign slowness which confers on the sound a hieratic immanence in which time and space are united in a single vibrant truth. The mystery of the Incarnation of the Word lies at the heart of the Christian faith. It is celebrated just after the longest night of the year, when (in the northern hemisphere) the days begin to lengthen until we reach the summer solstice, which is associated with the figure of John the Baptist. To celebrate this moment, the Church deploys an exceptional - virtually uninterrupted - liturgical cycle in which the usual Offices are interspersed with four Masses. The musical anthology presented here traverses some of the great moments of these four Masses of the Nativity. The music is that of the ancient chant of the Church of Rome, one of the oldest repertories of which traces have remained in the collective memory of mankind. Up to the thirteenth century this repertory accompanied the papal liturgy. It disappeared with the installation of the papacy in Avignon, and sank into oblivion. Rediscovered in the early twentieth century, it aroused little enthusiasm among musicians, and only began to be studied properly, first from the liturgical, then from the musicological perspective, in the second half of the century. At this time, to distinguish it from Gregorian chant, it was named ‘Old Roman chant’. Old Roman chant occupies a central position. It provides the key to the musical filiation between Jerusalem and the Greek heritage, while also enabling us to understand the treasures of Koranic cantillation.