Cableguys offers a fully functional 30-day trial of ShaperBox 3 (which includes VolumeShaper 4). This is the only free version.

Cableguys provides a free demo of their plugins that is not time-limited, though it has certain restrictions like only being able to use one instance per project and not saving settings.

Cableguys VolumeShaper 4 is a professional-grade volume modulation plugin primarily used for multiband sidechaining stutter effects

Sign up with your email (yes, it is really free) and download the installer.

: A "Magic" button that analyzes the sidechain input (e.g., your kick drum) and automatically draws the mathematically perfect curve to avoid frequency masking while preserving the sub-bass.