I'm going to drastically simplify because marketing is a LOT more than these two things, but when it comes to the PROMOTION area of Marketing, we can think of most activities as falling into two camps: brand building or user activation.
Brand building is the big picture. Nike is GREAT at this. Nike doesn't run ads about “get X shoe for 30% until the end of the month,” they run inspirational ads pitching the LIFESTYLE they stand for. Yes, their products are in it, but it's about reinforcing what they want you to think of when you think of Nike.
Activation is about trying to get someone to do a specific thing. “Apply for 0% financing between now and the end of the month,” or “Naco Fries are back for a limited time,” or “listen to our new album.”
Organic social media is great for brand building but often disappointing for activating your audience. Ever notice how pictures of puppies and attractive people at the beach and proposals get tons of traction but when you post a link you can't get people to engage? Some of that is human nature, but it's also how the platforms are designed.
Zuckerberg is running a business – a business of keeping user attention so they can sell ads. So they do everything in their power to keep people in their apps EXCEPT for if you've paid them money! It's why you can't put links in Instagram posts and it's why Facebook posts with links or Youtube videos get throttled by the algorithm – it's bad for business!
Like they actively make it hard for you to get people off their app. This is why posting “new song” or “new show” feels like yelling into a blackhole. Even if some people like it, the chance that anyone except your most diehard fans or closest friends will actually go through the effort to look up the song is slim.
My point with all of is to say keep posting stuff that grows your brand. Show your personality, make people feel like they know you and have developed a relationship with you. But don't expect organic social media to do you any favors when it comes time to actually ACTIVATE your audience into ACTION. You need tools specifically for activation like email, communities, and paid advertising.
To learn more about the marketing psychology of getting people to ACTION, check out this post on Music Marketing Psychology.