When you enter step notes for a drum sound, you can set the velocity value for each step to one of three values: Hard, Medium or Soft. This is done by setting the Dynamic switch before entering the note.
When the Medium value is selected, you can enter Hard notes by holding down [Shift] and clicking.
In the same way, you can enter Soft notes by holding down [Alt] and clicking. Note that this doesn't change the Dynamic setting on the device panel - it only affects the notes you enter.
When you use different dynamics, the resulting difference in the sound (loudness, pitch, etc.), is governed by the "VEL" knob settings for each drum channel.
If no velocity amount is set for a drum channel, it will play back the same, regardless of the Dynamic setting.
To change the dynamics for an already programmed step, set the switch to the dynamic value you wish to change it to and click on the step.
Note that if you are triggering Redrum via MIDI or from the main sequencer, the sounds will react to velocity like any other audio device. The Dynamic values are there to offer velocity control when using the built-in pattern sequencer.