Multiband Expander v4.

Multiband Expander splits a track through a phase-coherent three-band crossover and gives each band its own expander and threshold, so noise can be pushed down hard in one range and gently in another. That helps with hum on guitar tracks, and the same expanders can pull down softly played hits to change how a rhythm feels. Built-in SpectraFoo analysis makes the crossover points and thresholds easier to place. Version 4 adds VST3 on Mac and Windows, native Apple Silicon in VST hosts and undo/redo.