I: gives nokia vibes but in a good way
J: Good but repetitive
G: Gives a cool and calm vibe with those fire sounds and piano
H: It is a bit loud, nice rock beats but loud for a sound that is to be played in a background
F: This is the only one i listened to twice so that's a good sign, not sure if appropriate for a browser though
E: Don't know why but reminds me of Hitman
Might be a bit depressing when we listen many times, but can be a excitement redox which can be useful when doing work
C: Has a nice upbeat tone which raises excitement levels
B: Tells us it is a browser sound, obvious choice but Opera Gx is not an ordinary browser, it might select something else for uniqueness or this one for best experience.
A: A and B are similar but A is more suited for a game environment, could be better than B, let's leave it on the votes.