Something interesting happens to you as you become a better and better musician. Somehow, it's like the musicians become as real as their music, and you don't really feel like you need to meet them in person at all. You already are, in a song. Who they are is completely laid bare - you know, just because you now can, that the song you're listening to has been fiddled with so many times in so many different ways; dodged so many a bullet to become or stay the song you're listening to right now and none other. Such that the thinking process that left the song as it is completely bare. Whatever they left out is a clear oversight, intentional, or unintentional.
For example, take a musical "geniusmiracle", like the Beatles' "Yesterday".
While, I didn't like the Beatles, nor felt like I had to, "Dear Prudence" is like, kinda perfect to me. So I'm somewhat forgiving if a similar musical experience in their catalogue is what happened to everyone else, and then it became widespread belief that their music is sacredly in the territory of genius.
But there is no such thing as genius. Or rather, genius is as genius does. Unless you get creative yourself, I don't think there's a way to know that every time you sit down to create, all the ways to fuck up are still around from the last time. It's like how I describe my day job (software developer) - being good at it is like being a surgeon. It's a rookie mistake to leave a surgical tool inside a patient, but one you can make on any day of your career.
Music's the same. Michelangeli, famed for never missing a note, wasn't 100% accurate because he couldn't make a mistake, it's because he didn't want to, and so he did what he needed to make sure he didn't.
As for the job of designing music, and not just playing it, it's just really hard to say what's a 100% right decision about the music, and what's not. Take the Beatles' "Yesterday", which I introduced further upstream. 26 seconds into its two minutes five, a string quartet starts up. Ok, well, what are they doing? Nothing much really, they're taking up the theme of the melody, trying to blend in. Well, ok, you go, and keep going. But if you're like me, you don't drop the point.
Well, does the sound need that support? The Beatles, elsewhere, are fine with just a strummed guitar and voice combo. Their song "Blackbird", for instance, a great song of theirs, adds in the clacking of something wooden I'm not sure of, and field recordings of a bird. Simple, yet revolutionary. It's still pretty audacious to do something like put a field recording of a bird right across your whole song like that. Nobody's doing anything that fun on the radio, that's for sure. Yet it works, and we love the song.
"Yesterday" follows a similar story in terms of orchestration. The main thing is a guy singing, and a strummed guitar. What do they do differently this time? "The budget allows it, so let's put on a string quartet!" calls out someone in a British accent, (because I'm not sure which of them pulled the trigger).
Really?! A string quartet? But why? Is it just because classical music is fancy? As a classical musician, hogwash. If they sadly believed it, we now have inferior product they should have kept baking and gotten back to us later. But too late. Frozen in time forever, we have the rather irritating sound of a string quartet, as I hate the slightly nails-on-chalkboardy sound of a string quartet, unless there's a reason I'm ignoring that, because the music is doing something else that's cool.
It's said that people can't express what it is and what it isn't that they like or don't about a song. This isn't that it's impossible, but often because they just aren't trying to be observant. I think a significant part of getting better at music, no matter who you are, is trying to understand what is it that you like and don't like about what you hear. What I've done here isn't flying over anyone's head, is it? Listen to the song, and you can see what I'm talking about. Chances are you can't even remember the string quartet was in there, because your memory's doing you a favor.
I got into music because I thought there was something mysterious to chase after. In the end, there wasn't. Chasing inspiration is fun in whatever field you're in, but inspiration is as formless as the shape of your mind. It doesn't come packaged and labelled with opus number, even for geniuses. We know(?) this for ourselves, but assume differently for others.
Because of this, music is poorly understood, even by musicians, who often believe in some kind of musical magic. I have a fantastic piano teacher who certainly knows her stuff, but just like some Beatles fan might not allow you to dislike the song "Yesterday" because they're "geniuses", she has these sorts of unexamined musical verdicts about people called "Bach" instead. Ah well.