Hugo Riemann (1849-1919)

He systematized the discipline of musicology.  He led the way in a stylistic study of types and periods of music, a specialization that has resulted in a wealth of authoritative studies by contemporary musicologists.  The list of Riemann's writings is long, but most significant is the "Musik-Lexikon," (Leipzig, 1882), a work that has gone through many editions and is recognized as a standard reference in music.