The most recent addition I have made to the GMS is probability distributions for note pitches and durations. The way this works is that the user adjusts sliders from zero to one-hundred for each note in the twelve tone (chromatic) scale.
When note probability distributions are enabled, the randomness is weighted so that notes set to zero will never play while at one-hundred the note has the maximum probability of playing. This way the user can setup any sequence of notes in a scale or chord, then toss in a small (or large) possibility for an altered or dissonant note.
The same is true for duration probabilities except that I have the dotted durations as a separate possibility that is applied to the duration determined by the weighted random function. Here’s an example of the note and duration probability distributions in action with the settings as shown in the image.
GMS Probability Distributions