Lovely!  Pulling off a Duel of Songs is not easy, in either word or picture, and yet you've created a strangely peaceful yet powerful battle scene here.  The sobering reminders of the rising death toll keep it well grounded and quite somber, and yet there is no doubt of the outcome.  I like the idea of Iluvatar giving permission, and Manwe not giving obesience in his own house.  A delicate balance of power, and the disagreement between Ulmo and Orome fits them well. 

Thank you very much for sharing this unusual story!