Tolkien gives us astoundingly little information about the presumed 'magic' that the
Istari practice in
Middle-Earth. It is obvious that all three of them, who are accounted for, each have some sort of 'aura' that allows them to do their job:
Radagast has an aura of trust, kindness and love of nature which allows him to interact with the fauna of M-E;
Saruman has an aura of importance, leadership and councelling to help him manipulate his subjects; and
Gandalf has an aura of kindness and trust also, but also of immense knowledge and wisdom, as well as pure goodness. These 'auras' may have nothing to do with their magical skills, but rather with their practical and more 'social' skills, but it was just a thought of mine.
Anyway, as I was saying, Tolkien gives us absolutely no idea of what effect the saying of a 'spell' can have on surroundings or
objects, or people. Gandalf says a spell three times in the book (supposedly, although only two are certain): with the
wolves, with the fire, and (supposedly) with the door. But can we be sure that the 'Word of Command' is actually a spoken word? If the
Maiar coexist between the Seen and Unseen worlds, do they really need to speak the words in order for them to work? Perhaps Gandalf mumbled his thoughts, but the main 'spell' might have been a mental utterance which caused the door to do what he wanted it to do.
But what I mean is that we have little or no solid evidence to back up any argument about actual magical powers. Maybe the HoME have something, but I doubt it.