Little-known aspect of Theodor Billroth's work: his contribution to musical theory

Theodor Billroth's contribution to musical theory is discussed and evaluated. Billroth was a close friend of the composer Johannes Brahms and was himself extremely musical. At his death he left the manuscript of a book on musical theory, Wer ist-Musikalisch?, which had gone through four editions by 1912. In it he attempted to answer important questions on the nature of sound perception, the importance of rhythm as a fundamental element in music, the relation of pitch, tone, and volume, and the ways in which to account for the affective power of music. This article outlines the main concepts, contributions, and opinions offered by Billroth.