LumiComposer: Negotiating Creative Control Between Illumination, Mapping, and Generative Music Models

Real-time creative systems redistribute authorship across sensors, mappings, and generative models, yet modern optical standards reduce dynamic ambient light to static metrics such as hex color codes, stripping its temporal and sensory depth. To let people sense light more intuitively, we present LumiComposer, to our knowledge the first real-time spectral-to-music system that steers a streaming generative music model directly from ambient light, deployed on a custom hardware sensing device. The system pairs a continuous mapping from multi-band spectra to music attributes with an LLM-generated micro-poem that mediates between light and sound, forming a dual-path generative architecture. To evaluate this design, we conduct a user study on human preference: participants prefer poetically mediated audio over pure physical sonification $68.5\%$ of the time, with physical mapping grounding low-level acoustic properties and poetic imagery driving the affective congruence behind that preference. These results suggest that creative agency in real-time generative systems is not fixed but negotiated between deterministic physical mapping and generative poetic mediation.