"Free Chromaticism" is actually a much more accurate term than anything essentially aiming at looking at Williams' tonalities in a strictly modal perspective, or from the perspective of functional harmony. Simply because Williams almost never writes exclusively modal, nor is his music harmonically "functional" in any traditional sense. In other words, one might be "missing the point" in any attempt to find the logic behind Williams' melodic and harmonic constructs. At least if the point is understanding how Williams actually constructs these passages. Yes, we must have a complete and thorough understanding of modalities and functional harmony (and a whole host of other things), but the real reason why this information is helpful, is so we can observe how -in this case- Williams doesn't adhere to them, doesn't abide by them. The truth of the matter, is that this knowledge (and a great deal more!) becomes internalized as a myriad of sonic options, and gradually, through our experience writing and writing and writing, forms a language that gives us the freedom to shape music naturally and freely. This is how Williams' technique evolved, and it is how we all can evolve as practitioners of the craft of writing (and analyzing!) music.