Title say's it all...

No, just once.

That whole questline was a huge let down in my opinion.

I thought it happened once a week. Only have seen it once but I've seen the morning after. Pretty sure it's a recurring event, even Elisif says it will happen weekly

I think its one of those things that they say happens but actually doesnt. I only see it once after quest is done.

For me the people gather around outside every night and play music and that is it.