[Pitchwife]

As for 'fay' with an a, Rumil and Orald have summed it up pretty well.

Another argument for Tuvo as a proto-Maia (now that I've finally managed to get my hands on copy of BoLT and had a chance to look the whole story up): He seems to have had a pretty accurate idea as to what or who was sleeping in Murmenalda (or why else would he have forbidden his people to go there?), and unless he himself had previously stumbled across the sleepers much like Nuin did later, how could he know, if not by remembering a vague hint heard in the Music?
As Lalwende remarked, however, he doesn't really make an evil impression, with his forbidding Nuin to trouble the sleepers because he was scared of the wrath of Manwe or Ilúvatar himself - a consideration that wouldn't have kept any genuine disciple of Melko from causing any mischief he could. (It certainly didn't prevent Melkor himself in the later Silmarillion messing with the Children of Ilúvatar.)
So (to correct my earlier post) there isn't really that much evidence leading from Tuvo to Thû/Sauron, apart from the similarity of names and the rejected 'sorcerer's apprentice' note.

There is, however, another character in the outlines for Gilfanon's Tale who strikes me very much as proto-Sauronic: namely, Fukil/Fankil/Fangli, a servant of Melko's who escaped from the attack of the Gods on Utumna without getting caught and later corrupted most of the newly-awakened Men, turning them against the Elves of the Great Lands. That story rings a lot of bells for me, from Melkor's servants catching Elves near Cuiviénen in order to corrupt them into Orcs to Aranel's story of the Fall of Men in the Athrabeth...
Anyway, it seems our beloved Necromancer had a lot of ancestors...