After a moment, I decided that it would be easier to raise it by a half-step, at which point it became much easier to play on the guitar, moving into the very reasonable people's key of G -- as opposed to the annoying key of Gb. Which I suppose wouldn't go very well with wind chimes that were clearly in the key of C. And it's remarkably musical, although I have no idea what the tune was. It sounded vaguely classical, but that doesn't prove much...
But if that's what the mockingbird was singing, he had good taste. :)