Interestingly enough the Winterset sang Tar Barrel only last Saturday on the otherwise rather disappointing Thompson Family Christmas Concert. The entire 60 minutes, plus some bonus material, is still available - for another four days at any rate - on BBC Radio 2 Listen Again. But I agree, the words aren't all that easy to transcribe. (You'll also find the Unthanks performing the magnificent Farewell Regality on that programme (see separate thread)...)