The river sings

Yet another blorp: the thought that the river has its own voice, which concealed by the never ending spattering of water on the surface. But it's still there. When I do a spectral view on the recording at very fine grain then I can see that certain frequencies are stronger than others and that they are continuous. I made a filtering, leaving only those frequencies intact.

Listen [ here ]
and the original [ here ]

It's almost like singing, isn't it?