ATKTransientSplitter

ATKTransientSplitter is a mono transient splitter, cutting an input signal into its transient and sustain parts.
The plugin follows the implementation of the transient shaper with a twist explained on Audio Toolkit blog. The parameters are:

RMS is the size of the power windows.
Attack is the attack time constant for the slow attack/release filter.
Attack fraction (or ratio) is the percentage of the attack time constant that will be used for the fast attack/release filter. Used to work on the transient at the beginning of a sound.
Release is the release time constraint for the fast attack/release filter (as the release time has to be higher).
Release fraction (or ratio) is the percentage of the release time constant that will be used for the slow attack/release filter (as it has a faster release time constant). Used to work on the transient at the end of sound.
Threshold.
Slope is the ratio, 1 keeping the sustain at a constant RMS above the threshold, higher means that the sustain will be reduced by this factor (swell-like behavior).
Softness is an indicator of the harshness of the knee of the underlying swell.