I think there's a big difference between a "stoney" silence - solemn, po-faced etc etc - and an attentive one.

That might sound daft - silence is silence, after all - but it makes perfect sense to me.

An example, in terms of London folk clubs:

Sharps Folk Club, at Cecil Sharp House, Tuesdays. I've only been there the once, but I really must go again, because it had a really welcoming, friendly atmosphere. People were quiet while others sang and performed, but not so quiet that it was like a wake. People still quietly ordered drinks at the bar etc.

By contrast, the two occasions I went to Musical Traditions club, I really didn't enjoy the atmosphere at all: it felt much more like a "stony" silence to me. The atmosphere just felt ... mouldy. Way too conservative and formalised and procedural for me. More like a Quaker prayer meeting. Well, perhaps I'm exaggerating a little (I did enjoy the singing and performances there). Perhaps Quaker coffee morning would be a more accurate description.

I think the key is awareness of your surroundings. There's nothing more annoying than people who have no clue whatsoever that they are being annoying. Equally, some people are so stuck-up that they seem to resent so much as a sniff from their fellow audience members.