Before revision: According to Stern, his research in the "apperception of change" began a "decisive metamorphosis" in his understanding: See also Variator Medicine and Health Audiology Tuning Fork Cavity resonator External articles and further reading 141px|Tone variator with rack and pinion design.
After revision: According to Stern, his research in the "apperception of change" began a "decisive metamorphosis" in his understanding: See also Variator Medicine and Health Audiology Tuning Fork Cavity resonator External articles and further reading