People have many more choices now. Sure, there are a few elite concert halls and cathedrals which don't seem to get a shortage of people interested in organ music but for the majority of venues - that's a difficult time.
If you choose a concert which you would like to attend, you have to like at least one of these 4 things about it:
1. The music
2. The performer
3. The instrument
4. The venue
The problem is when a person doesn't know the music, nor the performer or the instrument or the venue. In other words, she doesn't have any personal ralationship with them. In this case chances that she will choose to come to that concert are very slim.
Of course, I'm only talking about a person who goes to concerts from time to time. But there a plenty of people who don't go to concerts whatsoever.
Then only her friends or relatives whom she trusts can convince her to come. No advertisement or marketing (in the traditional meaning of the word) can change her mind.
Another problem is that for our would-be listeners many of our concerts really don't differ that much one from another. Yes, there is a difference between the performers or music or instruments but in general, often they are average concerts for average listeners.
This tactic could have worked in times when there was only one concert a year in such a town. People simply didn't have a choice. Now if you are in a larger city, the listeners have abundance of choices. Plus there is an unlimited organ music supply on the Internet for everyone which makes the matter dramatically worse.
If you are the performer, you have only one solution - find 10 people who trust you and who can't live without organ music and offer them a concert which would be so unique and remarkable and live-changing that every one of them would feel compelled to bring 10 of their friends to your next concert. And each of these friends later would invite 10 of their friends.
So 10 x 10 x 10. That's how you spread the idea about organ music.