Does their presence there intonate that they are still "above it all" and can thus change things in the already created Music?
They can make no changes that do not have their source in Ilúvatar, and above that they can't change anything in the Music without Ilúvatar's consent. For instance, if Tuor being counted amongst Elves is such a 'change', Ilúvatar needed to be called for that.
After all, after the Music of the Ainur it was Ilúvatar who spoke 'Eä' and let things be. The Ainur did not have that power.
Give up the Halfring, she-elf...