TL;DR
Crafting machines emit different sounds based on the item they are crafting.What ?
Crafting machines could make sound according to the item they are crafting. For example, crafting iron bars from iron plates would make a metallic sound (like a repetitive hammering). Each item (or category of item) would have its own sound.Why ?
When walking through your factory, you see the various lines of products. It creates a kind of colorful mosaic. From a sound perspective, there is no such thing as you only hear the same sound of crafting machines, conveyors and inserters (and occasionnaly chemical plants). Such a feature would make sound be a mosaic as well.[Lot of work tho, for both the sound designer and the sound engineer taking care of blending with music.]
