"Randomize button selects a random component or generates a new one using randomizable synthesizers. It uses the same algorithm as drumset generator, but generates just the one component leaving the rest of the drumset intact. If you want to force using the generator instead of choosing predefined component, hold Ctrl.
Hold Ctrl to keep the original component, hence joining the new random component. This in fact behaves similarly to Load & join, but it uses a generated drumset.If you want to using the generator instead of choosing predefined component, hold Alt."
The bold bit should be deleted...comes from an older version and is superseded by what follows it.
Small point in the scheme of things...sorry.
double Ctrl meaning 
I'll check 