I headcanon that Elves and Ainur can mind-speak with each other, and for Ainur it can be a much deeper experience because they are spirits and their bodies (fánar) are unnecessary to their true nature, hence the comment about the mind being shielded.
Tulkas pounded across the land in his fury. That double-crossing, blackhearted... if Tulkas had his way, when Melkor was found he would be ripped limb from limb and his spirit thrown into the Void!
Suddenly he stopped. He could just make out a figure on the eastern shore of Aman, its mind shielded, yelling a fierce tirade in Valarin to the sky.
"Father, why? I asked for one thing, and you in all your wisdom and benevolence could not grant it me! This Arda is a sickening abomination!"
Tulkas inches closer to see that the figure is dressed all in black. He is clearly an Ainu from the glow of power about him- he does not recognize the fána- a disguise, no doubt- but he has evidence enough.
"Your words have sown poison enough, Marrer of Arda," Tulkas growls, sneaking up behind the figure and forcing it to the ground.
Clear blue eyes, full of tears, meet his. No matter the form they take, no Vala or Maia can change their eyes.
Tulkas jumps up in horror, but Manwë merely smiles sadly. "Aye, that I am," he whispers in a voice so faint that even Tulkas has to strain to hear him. "Aye, that I am."
Keep in mind, too, that the conclusion that it is Melkor on the beach saying these things is an absolutely valid one.
