Friedrich Ludwig belonged to the school of thought among cultural historians that did not ascribe to the Romantic view that Baroque Polyphony was the only type of polyphony of highest worth; rather, he sought to explore its historical development and evolution, leading to a critical reassessment of
earlier music. These researches have made the practice and theory of music of the Middle Ages accessible. His research area was music before
Palestrina-style polyphony; namely, the
Ars Antiqua,
Ars Nova, and the polyphony of the
Franco-Flemish school. As a historian, Ludwig was already familiar with the cultural unity of Europe in the
Late Middle Ages, and he approached it through the narrative and source-based methodology of
Leopold von Ranke, of whom Ludwig's teacher Bresslau was a disciple. These methods had, for instance, moved Slavic cultures into a new perspective. In contrast to the prevailing view among music historians of the 19th century - a view epitomized in
Wilhelm Friedrich Hegel's
Phenomenology of the Spirit (1807) asserting that music is an art in and of itself, Ludwig followed a systematic method to explore the relationships between music and other cultural phenomena such as architecture and literature, finding in it unity through the poetry of medieval languages. For this purpose, he used the
philology of High Middle German, the Romance languages, and medieval Latin, the
chorale, and historic chronicles. He made stylistic comparison of primary sources to date musical works, and introduced these methods to music historiography. Ludwig's contributions to musical scholarship include his investigations into
Organum, deciphering early
neumatic notation (square note notation), the discovery of
Rhythmic modes in the unison songs of the 13th century, and the systematic representation of compositions of the
Notre Dame School and the
motets of the
Ars Nova. He transcribed many multi-part works of the 15th century and published them in critical editions. Ludwig discovered the compositional principal of
isorhythm – a term he coined. He also coined the term
Stimmtausch. == Selected bibliography ==