Complex sentence: Mei was the first European after Boethius to do a detailed study of ancient Greek music theory, and wrote his findings in a major treatise, "De modis musicis antiquorum" (not formally published, but written 1568 to 1573).
Split into simpler sentences: Mei was the first European after Boethius to do a detailed study of ancient Greek music theory. He compiled his findings in a major treatise, "De modis musicis antiquorum" (not formally published, but written 1568 to 1573).