iTunes inherited a visualizer with its SoundJam MP ancestry and shipped one to every Mac and, later, Windows machine with an iPod: swirling particle nebulae responding gently to the library. For countless users it was the only music visualization they ever ran deliberately.
The 2008 refresh introduced Magnetosphere, a physics-flavored particle system originally by artist Robert Hodgin of the creative-coding world, bringing gallery-grade generative aesthetics to a default screen.
The bundled visualizer era faded with the app itself, its role dispersing to streaming canvases and dedicated tools. Its legacy is expectation: mainstream audiences assume music can simply become image, because for a decade it did, by default.