[Mithalwen]

I suppose at a basic level the answer has to be yes since an omnipotent creato has to be omnipotent however I don't know if he coukd change thee rules in something already created without destroying it is another thiing.though ... depends a bit on the changes.... like it is easy to dye whit cloth another colour but to change a dark colour light tou have to bleach it at potentiall damage the structure..

There was some discussion, I think on a thread started years ago on Music and magic, that suggested that because music was the essence of Arda's creation it could be used to create changes in Arda ~ magic effectively. I'd need to look it up but things like Felagund's song against Sauron, Galadriel singing of leaves of gold..but that is bending not breaking the rules maybe