Sans AU headcanons, because yes.

Nightmare headcanon #2

Nightmare is very into the 'dark academia' aesthetic, and does like to dress the part from time to time. He also likes classical music, seeing as he grew up listening to it, therefore it is obvious why his favourite musical instrument is the violin, and his second favourite being the piano. He of course can play both the violin and the piano, he sometimes does when he is feeling particularly miserable and down in the dumps, playing them makes him feel better.

Nightmare doesn't always wear his usual Sans-like outfit, as said before, he likes to wear any kind of clothing, minus dresses, to do with the dark academia aesthetic. Nightmare has quite the wardrobe of clothing, scratch that, it isn't even a wardrobe, its an entire room. Yes. Nightmare himself built an entire extra room in his bedroom in the mansion (From now on I'll probably call his house a mansion), just for the sake of space for more clothes. Though I must add that some members of the gang do like to steal his clothes from time to time seeing as he has so many. But you know, a Prince of Dreamtale has got to live up to his title . . . Albeit Dream doesn't as much as Nightmare, since Dream thinks he is not worthy of the title of 'Prince of Dreamtale', therefore he doesn't like to have people around him treat him like the royalty he actually is.

-I swear whenever I am listening to classical music, for instance right now, I always write differently than usual. Its odd. I just- Can't seem to help it-

-The song I'm listening to is called Reflections - Toshifumi Hinata. Its the one hour one with the rain. I just find it nice. I personally think Nightmare would love the song.

-Bean