Tying scroll or scale speed to a rising FFT band accelerates the visual motion through a build

The scroll/zoom-acceleration visual transition is triggered during a build, so the image’s motion accelerates with the audio riser. Scroll speed or scale is made to track a rising frequency band via a reactive thunk — highs push the scroll, bass breathes the zoom — so motion energy climbs with the audio. On the drop, the reactive thunks are replaced with a slower constant to settle into the main section. The move maps audio build energy directly onto visual motion energy without changing the visual source.

Examples

noise(3).scrollX(() => 0.02 + a.fft[3] * 0.3).scale(() => 1 + a.fft[0] * 0.4).out() — highs accelerate the scroll and bass breathes the zoom; on the drop, replace the thunks with slower constants.

Assessment

During a build, which band is used to push scroll versus zoom in the example, and why? What is done to the reactive thunks on the drop, and what effect does that have?