Hohneck and colleagues at Mannheim gave 43 patients two fifteen-minute sessions on a body monochord, tuned once to 432 Hz and once to 443 Hz — the pitch used by German professional orchestras — and measured cardiovascular parameters and mood scales before and after each.
Both tunings lowered heart rate and improved self-reported wellbeing. 432 Hz produced the larger heart-rate drop, raised heart-rate variability, and reduced vascular resistance and stiffness where 443 Hz did not; but for most measures the difference between the two arms was not statistically significant. The exception was pulse wave velocity, which fell more under 432 Hz and did differ significantly between arms. Most participants reported little anxiety or stress to begin with, which limits how far the mood results can move.
The authors are careful in the introduction about why they ran it: the usual rationale for 432 Hz is historical and philosophical, not empirical.