Attached is the source of Neverball's (or Neverputt's) audio code. It does not use Mix_MusicVoulme, but instead Mix_VolumeMusic, which I would assume to be the same (again correct me if I'm wrong).
There are a few references to Mix_Volume* in any case (not the pointer, just referencing any type of volume operation) so hopefully this helps you out.
Attached is the source of Neverball's (or Neverputt's) audio code. It does not use Mix_MusicVoulme, but instead Mix_VolumeMusic, which I would assume to be the same (again correct me if I'm wrong).
There are a few references to Mix_Volume* in any case (not the pointer, just referencing any type of volume operation) so hopefully this helps you out.
Thanks,
Jacob