I would suggest that, before making such a comment, you actually spend some time (not just one visit, but over a period of months) visiting our group, or another Sacred Harp group -- preferably several, to get a comparison of the culture in each group, which does differ a bit though the fundamentals remain the same.
I would also suggest that it is not fair to lump every small group of human beings together with every other small group, and state that they all have the same problems or characteristics.
We make a concerted effort to attract and welcome newcomers. But we are volunteers. Our group does not have an advertising budget. Twice a year we put up flyers for our convention; the rest of the time our information is available on our website. Sometimes we're given wonderful free publicity, such as in this blog. We rely on these things and on word of mouth.
Often, people find us on their own because, sometimes even without knowing it, they have been searching for Sacred Harp, and when they hear it, they say to themselves, "I HAVE to do this." So it isn't entirely our influence that gets people in the door.
I will say that in the Sacred Harp community as a whole, there is a great deal of discussion about ways we can make newcomers feel welcome.
Do a little in-person research before making a blanket comment.
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