All the sounds get mixed together as they approach you (as they compress the same air), by the time it gets to your ear it can be represented by one complex wave.

If you can build up intuition around Fourier decomposition I think it gets much easier to understand.

Multiple things going on at the same frequency are indistinguishable (up to a phase). Lots of stuff going on at different frequency can be separated. Light also has frequency (color) and volume (intensity)---it may be more intuitive to conceptualize in this way.

Yeah, waves add. Which, well they add from the center which looks weird and bumpy. What’s more amazing is how good our ears are at picking out differences (it’s like 100x more sensitive to differences than other senses) so it can tell what all those individual waves would be so we can still hear the guitar vs drums vs bass vs vocals when it’s all one wave combined.

But all sounds are vibration. If you capture the vibration, you capture all of the sound. The "different sounds" are all a single pattern of vibration; it's the brain and inner ear that decodes the vibration into separate sounds. And hence it can also be difficult to do, depending on what the sounds are.