you pick portal music v.1 I SAY THIS.....
I say this....2 is the best its upbeat and it keeps the traditional sound of the portal...3 is also nice for atmosphere... i say NG pick either 2 or 3...1 4 & 5 change too much of the traditional portal music and atmosphere. Or switch off between 2 and 3 or combine 2 and 3 to make the best music.