A recent day trip to the Main Headlands revealed an unexpected musical interlude when the wind whistled through the open pipes of a structure built near one of the old forts just north of the Golden Gate bridge. I Googled it when I got home, but couldn't find anything. I did however, find evidence of a Wave Organ built on a jetty east of the bridge – I'll have to check that out. I also found the Singing Ringing Tree in northern England and this video of the haunting sounds it makes.