How about applying real-time effects to the audio? Nothing heavy, but just so they're rarely or never exactly alike? Preferably adjusting the parameters depending on something to do with the event (for example, make the "starred" sound less high pass filtered the more projects the user doing the starring has)... and then add the ability to define and control said audio filters to sound packs. Of course this would increase client requirements by a lot, so maybe it would need to be optional. And/Or you could simply pre-render a bunch of variations and mix between two of them for each playback for more variety at next to no cost.
When we began, the idea was to synthesise everything, and have many perceptual variables to play with. Then we realised that we could validate the idea using pre-rendered sound snippets. We'll turn back to something more sophisticated once we start adding interfaces for levels and continuous measurement, and I'm sure that will wash through to more flexibility in discrete sounds as well.
i think, as I said above in the thread, something you could really benefit from is some quality reverbs, both to enhance the spatial image (different sounds would be in different locations of this virtual space, and thus get different reverb tails), as well as the fact that reverbs tend to push things into the background, wash them out a bit, and hopefully sort of mush/glue together sounds when they occur in short repetitive succession.
i just had another idea, and you just have to try this and see if it works or what it does: the exact millisecond when an event occurs is not that important. I think you can safely shift an event 20-50ms in time, without losing important accuracy. You could use this leeway to space similar events apart slightly, so they don't give that glitchy "retrigger" sound effect as much. It'd take some code, but you could even buffer all events for say 200ms, and use that sliding window to space them out as evenly as possible. I don't know if it would improve things, because it's really not what happens in physical ambient sounds, but it seems to me like it would smoothen things up a bit more. You could give it a try.
