I've been thinking about this a lot, Spaw, and thinking along the same lines as kat that mine would be a lullaby.I nearly went for 'Summertime' from Porgy and Bess but it should really be a song from my own tradition, so I'll take 'The Gartan Mother's Lullaby', full as it is of Celtic imagery and the spirit world, with many a story to tell if time allows.
Now this thread should be made into a book!!
Noreen