The reception of Wagner’s music as physically affecting, sound that manipulates the bodies of listeners, took place within a context of research into human and animal physiology. From reflex mechanisms to sense energies, the physiological response to art brought about new understandings of ‘physiological aesthetics’ in figures from Herbert Spencer to Thomas Huxley and Francis Galton, with a corresponding ‘physiological music theory’ applied by Ernst Mach and Hermann von Helmholtz. This led to various efforts at quantification of ear acuity and the role of the auditory nerve.

In the shadow of decadence, critical evaluation of works like Tristan and Tannhäuser traverse the spectrum from appreciation (‘bliss of the spinal cord’) to anxiousness (‘Wagner increases exhaustion’). Against these claims, Wagner’s numerous writings on sentience (Sinnlichkeit), rooted in Ludwig Feuerbach’s philosophy of perceptual realism, were directed towards topics as diverse as a theory of performance, the role of critics, and animal testing.