One thing I would mention about the FSGW's participatory events, which include our monthly Open Sings and our Getaway weekend, not to mention the informal parties and after-concert sing-arounds that spring up among our members:
We've got the concept of the sing-around, which is a little different than a sing-along. We go around the circle, and everyone is offered a chance to perform. They may sing or do an instrumental. It may have a chorus or it might be just a solo. If someone doesn't wish to sing, they can pass, or they are permitted to request something. Even the shyest people are encouraged to participate, and super-egotists (including commercial singer-songwriters) soon tire of showing up, because they'll only get a limited number of opportunities in an evening. The quality of the music may vary, but the social quality of the music thrives. "Newbies" learn because they are given the opportunity to practice performing. And the good among us get better--because the opportunities to share our songs come at regular intervals thoughout the year, we're encouraged to build and expand our repertoires so we don't bore ourselves (or our friends) with the same old same old every time. And we also learn the social skills of sharing music. Sometimes that means taking on responsibilities--deliberately singing a chorus song after a string of too many solos, or doing a fast piece after slow ones have made the group soporific, or responding with encouragement to a struggling beginner. Those social skills develop over time and in a community. But once you've got a critical mass that's used to a singaround (like the FSGW), you can incorporate people into it very easily--and they'll learn fast.