How hard is it to do sounds procedurally? For example:
It's certainly possible. Though I'm not good enough at audio to do it
I don't think I'd want to in this particular case anyway, because I'm going for a more "realistic" sound atmosphere while procedural sound tends to be more synthetic. That's referring to completely procedural sound, instead of semi-procedural sound that is increasingly common in AAA games these days, having a professional create content in a full sound engine like FMOD, and integrate it into the code to modify things on the fly. Pretty amazing stuff, but it absolutely really requires an experienced dedicated sound technician to do.
What I've done instead is include engine support for a huge range of different sound samples in different situations, as you describe. It's something that already exists in X@COM, where things like bullets, and even ejected casings, sounding different depending on the type of material they hit. I don't need to make as much use of it in Cogmind because there are far fewer materials, but it's really helpful in X@COM where it's important to be able to handle a variety of environments realistically.
It's been a while since I fired up x@com, or looked through the files. From memory they were pretty good and added a lot to the atmosphere and feeling (it's amazing how much sound adds to any game). It might have also been the emotional attachment to the effect of some weapons with the particle system providing the visual feedback (RL purists be damned. My rocket launcher should actually go boom, the text interface doesn't have to tell me it did, it just goes boom through the speakers). X@com also had a fair bit of sound discovery appeal due to some slightly non-canon weapons ("Squeeee! A chain-gun laser!") that could have sounded like crap and still been awesome.
I'll go through the files, but they all sounded pretty good in my opinion. I'm not exactly professional in this context either. Rough, ready and quick, slightly knowledgeable and experienced, but by no means a professional ear to judge quality by.
Yep, amazing how much sound added to the game. I think feedback and immersion are the most important things it brings to the experience, which makes roguelikes all that much better. Unfortunately few devs tackle it.
And your opinion on X@COM's sound would still be very valuable, in my opinion
One reason I'm not *too* worried about having super awesome high-quality sounds is that I can get away with less given the emulated terminal and ASCII particle effects, as you point out. Obviously I want them to be "good," but they're not going to win any awards for sound design.