Here's a question that came to my mind (I do not know if there is a correct answer but if there is no known answer perhaps we can speculate here):

If you are both a Nightingale AND a werewolf at the same time (which is possible in Skyrim), and you die, to whom does your soul belong? Hircine or Nocturnal?

Thought this might be interesting

This has been discussed several times before. There's even a http://www.gamesas.com/topic/1365185-followers-of-multiple-daedra/ here in the Lore forum which answers that question.

Pretty sure Hircine gets priority. After all, were-creatures are solely his, until further notice.

Aka because your dragon soul is a subgradient of him.

Talos because you (might) be a Shezarrine.

[NUMMIT]'s gonna get real in the Aurbis's metaphysics.

The Ideal Masters.