Archtune is the combination of the Orchestal music + Chiptune with a few special synth elements made for the genre.
It was first used in the Terraria soundtrack made by Scott Lloyd Shelly.
Here is some examples of this genre...
Day: This theme is a happy tune with some orchestra to showcase a day theme.. It's main element is a 8-bit type Pluck.
Night: This theme is a bit darker with a more nightime type theme.
Underworld: A dark track with some Dubstep wobbles incorporated.
Bosstheme soundtracks: (WIP)