"I have found Crosby's tune, or 'air' 'The Unfortunate Rake'

Its in 6/8 and a minor key, with root E. Not easy to sing the words of 'The Unfortunate Lad' to it."

Interesting - thanks for the link.

There's no great problem fitting the words to it - at least one English collected version is barred in 6:8, though 3:4 is more general. However, although I can see superficial resemblances with the collected tunes, they don't seem very strong to me.