I heard a BBC Radio programme about this phenomenon, a French scientist was convinced that the silica had to have a coating of salt and a certain humidity to 'sing'. See also http://en.wikipedia.org/wiki/Singing_sands
This is a great recording. I'm working for a not-for-profit organisation producing some short videos for Northumberland National Park. One of them is about uses of the landscape and this recording would be brilliant for adding some subtle atmosphere.
I can email you details of the project if required - tried linking but rejected as spam.
Can I have your permission to use it? I'll attribute it in the end credits.
This is the purest, clearest recording of a single skylark...pure music to my ears. using this recording to help counter act tinnitus. Thanks Benboncan. (Just as Rogers and Hammerstein wrote "the sweet silver song of the lark")