That’s a fascinating idea—kind of like a biological bass line! If we could map the beat‑to‑beat variations of a user’s heart rate and feed that into the audio engine, the soundtrack could subtly shift tempo or texture in real time, matching the physiological state. We’d need a low‑latency heart‑rate sensor, a way to extract the instantaneous frequency, and a responsive audio synthesis pipeline. It’d add a layer of immersion that feels both natural and personalized. Worth experimenting with—maybe start with a small study to see how people react.