This is a concept for Dragon Cave, suggested by Hawktalon. It is not to be used elsewhere.
The Harptail is born with a few long thick hairs on its tail. As the dragon grows, these hairs eventually fuse to form the strings of a "harp". A dragon plucks the strings to find a mate that complements his/her unique melody. While the female has a lyre-like tail, the male's tail is more reminiscent of a concert harp.