Sound is an important (but often overlooked) element to area design. Beyond setting mood, sounds can foreshadow coming encounters, indicate hidden dangers, or serve as clues to the location of important features, just as a few examples.
A quick search of the vault reveals that many people have musical talent and have shared it with the NWN community, far fewer are willing to voice act, and the most neglected catagory is other sound effects... and this makes sense: far more people have musical tallent, some have tallent for voice work, but very few consider themselves foley artist, let alone know what one is.
Music is the fastest and easiest way to set mood, as long as you can find music to suit the mood you want. The problem with using music to set mood (in my opinion) is that it creates a cinematic experience, not an immersive experience. If you as a module designer want to tell a story, and view the players as an interactive audience, the cinematic experience is ideal, but if you desire to draw the players into your 'reality', one might want to avoid or at least minimize the use of music to places where it might actually be heard.
Although the kobold orchestra is re-known for their exciting dungeon combat music.Voice acting can help set mood or tell a story, but can quickly become a distraction. The ambient sound tracks for city, town, and tavern, include voice work meant to create the sense of a groups of people speaking, or 'Walla' - an onomatopoeia of the sound of groups of people speaking amongst themselves. Generally, one should not be able to make out entire phrases or sentences in walla, just stray words and inflections to give it a sense of realism. In radio productions, walla does not usually contain intelligible words at all, only murmuring. In NWN, the intelligible voices of the ambient audio tracks distracting for the same reason that professionally it is avoided. It draws attention to the sound, and as one hears the same phrases repeated more and more often, it erodes the sense of immersion that one as a builder is normally trying to achieve. Placeable voices have similar problems, but through precise or limited use can be effective tools for mood and story. Over-the-top accents or comical tones in voice work can quickly turn them into a liability though, unless they match the tone of the module.
Finally, sound effects. Nothing helps paints an immersive picture quicker than good sound effect layering: the rustle of leaves, wind in the trees, and distant animal cries. The sounds provided with NWN are good enough, but many have inconsistent recording levels, and some are simply bad. Recording good sound effects takes good equipment and knowledge of recording that not even most musicians and singers have, it is the domain of sound engineers and foley artists, and it explains why so few good new sound effects have made it into the NWN Vault.
I have explained some of my back-ground understanding of sound to help the dialog along, but what I am really interested in is what sort of sound-design philosophies and techniques do you fellow builders like to employ to make for richer environments, engrossing stories, and immersive experiences?
TL:DR '>
What kind of strategies and tricks do you use to paint with sound?