Valve has finally released the 3rd and final part of the Portal 2 official soundtrack, giving you an option to download parts 1,2 and 3 or all of them combined in download.
Portal 2 Songs To Test By website – Here
Download the complete OST – Here
Download Portal 2 Songs To Test By 1 – Here
Download Portal 2 Songs To Test By 2 – Here
Download Portal 2 Songs To Test By 3 – Here