Hi All!

Odd sort of question here....what are the copyright issues with using Trad lyrics?
Here's the back ground: I have a cd here by the GovernmentRams from NFLD and there is a song that's called "Parting Glass" and I want to use one of the lines in the refrain in a needlework piece I am designing.
Now I have tried repeatedly, over the course of two years to get ahold of this band, it management or a represtitive from the record company to gain permission to no avail, I get absolutely no replies.
A friend of mine says that Trad songs are "public Domain" and I should feel free to use the line.
ANy ideas, either on how to get permission to use the line or if it is true that Trad songs are "Public Domain"