Dead Sister: Beat the Turtle Drum

Since the Shelf Discovery Challenge is about to end, I have to hurry up and review the books I read. My Chapter 4 pick was Beat the Turtle Drum, by Constance C. Green, about two sisters who are good friends. Joss, the younger girl, is ready to celebrate her birthday with the gift of a horse in the garage for a week. The sisters are shown as good friends; different enough to irritate each other sometimes but also loyal and valuing their respective strengths. So it's rather sad when one sister falls out of a tree and dies (while the older one watches).The rest of the book covers the grief of the family, shock and rage and disbelief and denial and through to a hope of acceptance. It's a well done book, with little sentimentality but a lot of telling detail. I would have hated it as a child because I had a little sister and I would not want to practice her death. I wonder if I read it and managed to forget it? I did have a bit of deja vu as I read.I do have one question -- what is a turtle drum? Did I just miss that? B