A.D. 521 Written in the sixth century, the treatise De Institutione Musica by Roman philosopher and scholar Boethius (A.D. 480-525) explained ancient Greek music, which was primarily built on single melodies. In the treatise he assigned letters to pitch levels, leading to the modern A to G scale, and discussed consonance, scales, and the intervals between pitches. Boethius also adhered to the classical idea that music was intertwined with all disciplines. His work was particularly influential to scholars of the medieval period (500-1500), who considered Boethius the authority on music theory. His treatise led the way for the emergence of printed music in Europe in 1465. A century later, in 1558, Italian Renaissance composer and music theorist Gioseffo Zarlino (1517-1590) defined the modern major and minor scales that are still used today. His writings spread through Europe at the end of the16th century and influenced the next generation of musicians, who began composing in the Early Baroque style.