One of my friends recently asked how a song goes from mind to “paper.” And I think the answer is relative to your experience.
When I first started writing music, the song I imagined was always different than the song that came out. Radically different. And I never really cared because hearing a song in my head was just a cue to write.
I imagine that people who have been writing music for dozens of years are able to spit out the exact song that they want. And there are aspects of music that I can align exactly from imagination to paper, but some of it still remains ambiguous to me. Instead of hearing a step up bass line with a I III IV #Vdim chord progression, I feel an optimism with a tinge of yearning… but same thing, right?