HIEROS (in ancient Greek: sacred), performed by the vocal trio of Ensemble Céladon, opens up a musical reflection by alternating medieval music with contemporary composition. With this first album sung entirely a cappella, the ensemble, led by Paulin Bündgen, examines the definition of the ‘sacred’ and its evolution through the centuries. From the thirteenth-century conductus of the School of Notre-Dame to the six works of Jean-Philippe Goude, how has this sentiment, which inhabited and guided the artists of the Middle Ages, evolved? What meaning and place does our modern world give it? As is often the case, the answer becomes tangible when formulated in music.