Audio-reactive means causally connected: the software listens, extracts levels, bands, and events, and maps them onto visual parameters. The kick is not near the flash; the kick causes it.
Quality separates on two axes. Analysis depth: level-only systems pulse, band-and-onset systems play. And mapping taste: what reacts to what, how much, how fast. Loudness to brightness reads as natural; every mapping beyond that is authored, and the authoring is the art.
The approach’s promise is a show that is always in time without an operator. Its risk is monotony, which is why serious systems (Photism included) reserve big events for structural change rather than letting everything wiggle equally forever.