Thanks to all of you for your illuminating replies. It seems to me that there are autodidacts (some have to be because they are hard up), some who can learn to compose well given the right teacher, and some who, in spite of technical mastery (of harmony, counterpoint etc) will never learn to compose well. I suppose we would say simply that such people have no talent for composing.

And I can tell you that technical mastery doesn't seem to be a pre-requisite, either.

My position on this is that it can depend on the level we are talking about. A certain amount of basic technical know-how can be useful for a level 1/2 undergrad student, but really, across the board from level 1 to PhD, teaching (in the strictest didactic sense) is not possible (because, as Richard says, all students are, and should be encouraged to be, different). I prefer to approach the situation by creating an atmosphere wherein any student (regardless of aesthetic or stylistic persuasion) can feel comfortable and enthused to be creative on their own terms. This seems infinitely more useful (for student and tutor) than creating cones of oneself a la Donatoni...My tuppenceworth anyway...

Good casting - Aykroyd was a particularly apt choice to portray Donatoni during his Joyous Period.