ABSTRACT
Johann Mattheson's early absorption of John Locke's sensationalist psychology is remarkable coming when it did. Variations of Nicomachus's definition of phthongos can be traced from Ptolemy and Capella in the early Christian era through to Glareanus and Zarlino in the 16th century. In an angry and characteristically blustery essay entitled "Die neue Zahl-Theorie", Mattheson condemned Leonhard Euler's ideas in no uncertain terms and admonished potential readers to steer clear of such mathematical nonsense. Like Euler, both Mersenne and Descartes believed that the mathematical simplicity of an interval's frequency ratio determines its consonance ranking. The new Klang-Lehre that Mattheson proposes turns out to be nothing less than one of the first modern-day phenomenologically-based theories of tone perception. For Mattheson, there could be no debate as to the respective importance of ratio and sensus. Mattheson was certainly grateful for Johann Adolph Scheibe's support—at one point even referring to him as his "General Lieutenant.".
