You didn't specify which game (Qube or Qube 2) but since Qube doesn't come with a soundtrack or have a "season pass" option, I'll assume you mean Qube 2.
There are two ways to download games from GOG.
1. Using Galaxy, the GOG client (similar to Steam). I can't help you with this. I've never used it. I'm not even sure if you can download extras with Galaxy. The soundtrack is an extra.
2. On the GOG website. Log in to the gog.com website (which you already know how to do since you've posted this question on the forum).
- After logging in, hover your mouse cursor over your user name at the top of the page.
- then, select --Games-- from the menu.
Your game list will appear.
-Click on the game you want (Qube 2 Season Pass).
Soundtracks are considered EXTRAS, they are NOT considered part of the main game and will not be downloaded with the game. Extras are downloaded separately.
So, you will now see two columns. On the left is the download for the game installers. The column on the right is for extras (such as avatars, wallpapers, and soundtracks).
Click on the soundtrack in the right column and download it with your browser. Depending on how you've configured your browser and what operating system you're using, you might be able to choose where to download the file or it might be automatically saved in a downloads folder or something similar. The soundtrack will be a zip file. You will need to unpack the zip file before you can access and play the soundtrack as mp3 files or FLAC files (whichever you chose to download).
Again, you most likely need to download the soundtrack by logging into the GOG website using your browser (firefox, chrome, opera, or whatever browser you're using). How that works will depend on the browser and how you've configured it.
Thanks. That worked. Don't know why that complicated as with a other game it downloaded it onto the games folder.