From the original musical sources he had collected, he merely drew up descriptions based on attentive observation, resulting in him being heavily criticised by those who considered him more as a clever collector than as an historian. He proved the scientific value of facsimiles of manuscripts, but also made his own transcriptions into modern notation. His "Scriptorum de musica", a compilation of writings (most of them in Latin) of several theoreticians of ancient music, is his most important work. He also established several critical editions of ancient music, including liturgical dramas from the Middle Ages and works by Adam de la Halle.