The “Dynamics” slider is used for broad control over the loaded preset’s timbre. By default it is mapped to the mod wheel (MIDI CC 1) but can be reassigned if you wish: How do I map my MIDI Controller in Splice INSTRUMENT?
It’s actual functionality varies depending on the preset that you have loaded, but will generally fall into one of three categories.
Dynamic Crossfading
Musical Effects
Velocity Floor
Dynamic Crossfading:
This is when the slider is used to fade between different dynamic layers, or “volumes” of playing. The approach is how virtual instruments such as those from Spitfire Audio are created, musicians are recorded playing at multiple dynamic levels (p, mp, mf, f, etc.) and then this slider gradually and smoothly fades between those different recordings. This allows for expressive playback by the user and can be used for phrasing and shaping. You’ll find this on most of the packs that are based on real acoustic instruments such as strings, winds, or brass.
Musical Effect:
For many of the synth and drum based patches, the Dynamics slider will control a curated and designed effect such as adding distortion/saturation, delay, reverb, chorus, flange, granular effects, and more.
Velocity Floor:
When used on acoustic instrument patches that respond primarily to velocity such as pianos, harps, and mallet percussion, this slider will affect the lowest possible velocity that you can reach. This allows you to play much higher velocity ranges without the need to slam on the MIDI keyboard. This functionality does not apply to most of the drum kit based patches, as those will often have a Musical Effect in place instead.