Almost every game has background music. There must be working example scripts on how to change the volume! It seems I need to hire someone on Elance to get a working script. I already posted a job listing for this and other tricky questions. I assume a programmer fluent in Unity3D JS could type this code in less than 5 minutes. I already wasted a day on this, which is way to much time.
Problem is, the music is started with the startup screen, obviously. It’s attached to an object with DoNotDestroy script, so it keeps playing when scenes change. Now, changing the volume from the settings screen of the game just is the hard problem. Should that not be in standard Q&A, or a script that is included with Unity3D, since pretty much everyone needs that?