The latter 19th century saw the development of modern music psychology alongside the emergence of a general empirical psychology, one which passed through similar stages of development. The first was structuralist psychology, led by Wilhelm Wundt, which sought to break down experience into its smallest definable parts. This expanded upon previous centuries of acoustic study, and included Helmholtz developing the resonator to isolate and understand pure and complex tones and their perception, the philosopher Carl Stumpf using church organs and his own musical experience to explore timbre and absolute pitch, and Wundt himself associating the experience of rhythm with kinesthetic tension and relaxation.[5]