Video/computer games (most? all?) function similarly enough in time to the way that music does (particularly improvised music) that they can themselves be considered music, or, at the very least, musically meaningful play structures. I've thought about this idea enough now that I'd consider it a truism, and that it isn't apparent to everyone seems due, in large part, to the fact that game soundtracks have so far done very little to reveal the extent of this musicality.
To be clear here, I think there's a simple formula that can be followed, that has not yet been pursued with any seriousness (or playfulness), that will help begin to reveal the music that lies latent in games:
For every change of state in a game, there should be a corresponding change of state in its soundtrack.
As presented, this is hardly a novel idea except for the inclusion of one word: "every" (which can be substituted with "as many as possible" when dealing with technical limitations).
Recent games such as Mario Galaxy and Portal 2 (and more) have done some exceptional micro-studies in musical interactivity, with certain segments/levels mapping game events and processes to the soundtrack exactly the way that I'd like. However, they can't have mapped more than, say, 5% of game events to musical events, and as such, the musical interactivity becomes a novelty, rather than, as it ought to be, the articulation of a new expressive language.
It's as if, during a game of basketball, there was a 5 minute "experimental" interlude that accompanied all players' actions with a dynamic/improvised soundtrack by the pep band-- this would, without a doubt, be my favorite bit of the game, but it would also be a disappointment in that it didn't take that idea as far as it would stretch, to establish a new kind of basketball, an entirely new formal language, an improvised ballet of a sort.
Or, if this example is, itself, too novel, it's also as if early humans making vocal sounds, developing a spoken language of signs, for a moment produced sustained tones in unison, singing a perfect fifth--the beginnings of harmony--and then laughed it off, surprised at the unexpected beauty of it all, yet unwilling to continue to explore for longer than 10 seconds, unwilling to discover the language of music itself.
As pioneers of this new language-- musical gameplay-- games such as Mario Galaxy and Portal 2 ought to be celebrated; as ideals, however, they ought to be tossed aside as garbage, having done only a small fraction of the work (and play) that's necessary.