Nightcore is an unofficial sub-genre of Dance/Trance/Techno songs. A Nightcore song has to feel and sound similar to that of the original Nightcore group, otherwise it cannot be called Nightcore. You can read more about this by following the links below.
What is Nightcore? - A fairly in-depth but somewhat dated thread explaining the ins and outs of the genre. See this first!
Why Nightcore is sped up dance/trance not sped up any song
The definition of Nightcore - A massively in-depth explanation regarding the genre and why it is what it is.
How to make Nightcore - Also explains what kind of genre can be used
Still not sure what nightcore should sound like? Check the links below for examples.
Nightcore radio station:
Popular Nightcore YouTube channels: