I heard Martin Carthy sing his version of this ballad at the National Folk Music Festival (Sutton Bonnington) a couple of years ago; I'm sure he said that the tune that he used was Basque.
For another version of this ballad, see the version sung by Alison McMorland on the CD 'Ballad Tree' by Alison and Geordie McIntyre (The Tradition Bearers Series LTCD 1050, 2003). This is a wonderful CD of classic ballads, beautifully sung - highly recommended!
I've always thought that the eerie line, 'the channerin worm doth chide' refers to the impatience of the worms in the grave who are keen to get back to digesting the mortal remains of the 3 dead sons.