Music is almost always built up of multiple parts all layered together, to create a cohesive whole.
In modern music production there’s what’s called a “multi-track” recording where each part has its own independent recording and can be heard or adjusted in isolation before creating the final stereo mix.
Without active listening you’ll typically hear just that final mix, the “whole” which all the individual parts combine into. One big mass of sound. Maybe one or two parts stand out to you, such as the vocals or the instrument you play yourself, but it’s mostly one big sound.
Can you imagine being able to hear each and every layer clearly?
Like your ear is actually hearing all the individual multitrack parts independently as well as how they combine together to create the overall sound?