If you’re looking to add some dynamism and life to your music - but don’t want to pay for the privilege - then Caelum Audio's Flux Mini could be your next free plugin. Available for Mac and iPadOS in VST/AU/AUv3 formats, this lets you shape either amplitude or high-pass/low-pass filters simply by clicking and dragging on a graph.
You can add emphasis to the frequency modulation using the Emphasis knob, and there are 20 presets to get you started. There’s adjustable tempo sync, too, along with a Mix knob.
With its simple, visual interface, Flux Mini could be just the thing for everything from “simple sidechaining to manic modulation”. Find out more on the Caelum Audio website.