Well I came across an idea. You think of texture packs as an add on to the game. Well, what about a sound pack? Similar to the idea of a texture pack you could edit the sound of a noise in the game. I know that most sounds are only 1 second (I think almost are all) and I don't know if this is possible but the only way i could think of is editing it, by making another sound of 1 second, or replacing it, possibly as long as you want. I don't know when this could be helpful but if you're making lets say a modern town, for example, and want to edit the sound of a villager (townsmen) to your own voice or just a clip of someone talking. These are details that could bring out maps. Tell me in the comments if you think its worth anything, or if you think it could work. again just an idea ;p
Very hard to implement tough...
Stay fluffy~
http://www.minecraftforum.net/news/875-custom-minecraft-soundpack-man-made-mouth-noises/