OK, here's the info from Child. The Pentangle song seems to be a
conflation of two Child ballads, #1 "Riddles Wisely Expounded" and
#10 "The Twa Sisters". The first few verses and the refrain are
taken from #1 and the bulk of the story from #10.
In #1 the Knight takes the youngest sister (of three) to bed, and in
the morning makes her answer three riddles before he'll agree to
marry her.
In #10 the elder (ugly) sister murders the younger out of jealousy
by drowning her. The body is washed ashore and discovered by a bunch
of passing musicians who take various bits of her and make a musical
instrument from it (as one does under those circumstances). Later,
they play a gig at the elder sister's wedding and the instrument starts
singing and blows the gaff on the murderess.
According to Child, #10 is popular in Scandinavia, and he lists 12 versions
from Norway, 10 from Denmark, 12 from Sweden, 2 from Iceland and 4 from
Faroe. It's also been collected in Poland, Estonia and Slovakia. He
gives English words for 21 (mostly Scots) versions.
Phil Taylor
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