I don’t know if I’m dumb and never noticed this before but if you pause the game in a fight right now and scroll through the menu it plays a killer instinct chime.
It is an easter egg(I think). It plays the KI theme.
Has it always been like this? I feel like I would’ve noticed earlier.
I think it always had this.
Damn. i’ve played a lot of KI and never noticed this rofl. Oh well.
Hahaha, yea its been in the game since the beginning. Its one of the more subtle awesome things about this game.
There are TONS of Easter eggs in this game. Try and find them all! I’ll give you one though. ALL of the characters themes have “The Instinct” or a variation of them. Like for example, Thunder’s. Listen to his flute part VERY Closely. It’s fun scouting them out! 
(“The Instinct” is the official name of the KI Theme)