VirginiaTam, technically you are correct. However the premises should have a licence from the Performing Rights Society which allows you to perform copyright material to which PRS administers the rights.

In theory, a proportion of the licence fee is supposed to find its way back to the composer. However the admin is so inefficient that it is doubtful whether this is very effective so far as folk music is concerned.

Where the composer is not a member of the PRS then in theory you should seek their permission. In practice this is seldom done, unless its for a commercial recording or you happen to know the composer. It's fairly safe to assume that if a composer was that bothered about asserting his rights he'd join the PRS. Most in the folk world seem just to be happy to get their material performed.

Controversially, PRS also claims a right to licence premises where non-copyright material is being performed, on the grounds that copyright material might be sung (do you know the copyright status of all the songs you sing? "Happy Birthday" is copyrighted, as the post following yours noted)

There are plenty of threads about PRS if you care to search for them and don't lose the will to live.