The creative process starts and ends with professional, respectful collaboration. Discussions with the game director, creative director, art director, et al - being a part of the script writing and voice casting / recording, all the way through production, gradually building up all elements of the soundtrack.
This approach allows everyone to investigate, to try various solutions with sound and visuals before settling on anything final. An important distinction with the creative collaborative work field of film and games is that any sound production or post-production is the culmination of a collaborative creative team’s ongoing work together, and not an animator, designer, artist, sound effects designer or composer working alone and handing finished work over to the next person in line.
Because we work in different dimensions, we can work together on the shaping the same thing at the same time. Sound is interesting (and inherently challenging) as it relies heavily on the notion of other work being ‘finished’ before it can be ‘finished’. The collaborative team recognizes that sound is involved all the way through the shaping process, and not just the end.
When the final mix* is reached, there are still a lot of critical creative decisions that need to be made, usually in terms of what to favour at any given moment, voice, FX or music, but mostly about ‘clarity’. These are decisions that need to work with the story, character point of view and gameplay intensity, and so again, the discussions and ideation around what will work should continue to be collaborative with the production team during this time.
Getting the right people in at the right time can be complicated, politically, geographically and temporally (these same people who need to be a part of the process, very often also need to be a part of the process elsewhere).
What has always impressed me about film sound mixes, is the presence of the director and other deeply invested parties. Not only is this a welcome presence, it is absolutely a necessary one. This points to what a final mix really is all about, and that is the honing and sharpening of the intended experience for the audience. The technical aspects of the mix, the complexities of loudness, panning, levels, mix downs and measurements, though present and most assuredly being catered for, are (generally) not the topics for discussion with a director during a film mix.
I think that in games, finding these valuable collaborators is considerably more difficult, they should be the primary stakeholders, essentially the people who care about the totality of the final product - and i’d like to think it would be obvious by the time that you reach the final mix, in whatever form that takes, who these people are.
Even if there is literally no-one available, it is very important to have someone to collaborate with on a mix. Whether that is another mixer, a sound designer, the janitor (i'm only partly joking here, if they think the music is too loud and they comment that they can't hear the dialogue, that may be the biggest piece of help you'll ever get) - it is critical to have other perspectives and discussions during this period.
I would suggest members of the core-IP team would fit the bill here, however, the timing of any kind of final mix on a game production is crucial here, as these people are inherently ‘crazy busy’ at this time too. This notion of collaboration is something I’m always working on with every team and every project, and I think that if collaboration and trust is present from the beginning of the project, then by the end, the collaboration on the mix will be less complicated. What I would say is that any mix that involves multiple collaborators needs to be run in a very professional manner, almost as though it were an extended meeting. Keeping things moving, keeping attention on sound, discussing important points, tabling and making notes and action items of lesser notes. Anyone not contributing, or listening, should probably stop looking at their iPhone and leave the room. It can certainly complicate the mix if these sessions start to drag and bog down any meaningful progress, so assess the contributors on a day to day basis. Perhaps try out a larger group to identify valuable (and interested) contributors, and then whittle that group down as the days go by, or have one day per week where the group comes in to contribute.
Finally, this collaboration is about making a better game, so remember, some of the most valuable contributions of a mix come from discussions around the content, character pov, emotion, an intention or part of the story or gameplay that may be getting lost, or has been misinterpreted by the sound design, and can be clarified and (usually) addressed. A mix is about so much more than volume levels. It is as much a part, if not the crowing moment, of a long collaborative journey.
* A final mix is perhaps best defined as the last opportunity to make changes to the sound (aside from bug fixes) - in games, the mix is certainly something that slowly comes together milestone by milestone, feature by feature, and is not all left until the last minute to provide any kind of balance. I would generally expect a game to be rough mixed, and pre-mixes in any kind of run up to a final mix, and ongoing feedback, tweaking and collaboaration is all a part of that lengthier process. It is also still only likely to occur in any significant way on the bigger budget, AAA-title productions due to intense scheduling and focus on a console-based listening environment.