Tuor personally saw Ulmo blowing his horn, which made him see all the waters of the world in a vision.
And thereupon Ulmo lifted up a mighty horn, and blew upon it a single great note, to which the roaring of the storm was but a windflaw upon a lake.
—Unfinished Tales, "Of Tuor and his Coming to Gondolin"
Obscure. However see etymology of the name "Ulmo".