I posted a tribute to the 50th anniversary of the Cape Cod National Seashore a few weeks ago. My oldest daughter sent me a link to a couple of radio interviews on the anniversary as well so I pass on that link here.
One interviewee was Steve Wilkes, a professor at the Berklee College of Music in Boston. Wilkes has a project taping audio clips on Cape Cod. Follow the "Hear Cape Cod" link to his web page and click on "Map Index" in the right hand column that takes you to his satellitee map of all of Cape Cod . If you zoom in and click on either of two location markers that represent sites on the outer (Atlantic) beach in Wellfleet and Truro, you can hear the surf that I described in my original post. The Truro recording is especially good for this - melodic. You're getting sleepy, sleepy.....
South Wellfleet - map marker labeled "Marconi Station" (this is just down the beach from Le Count Hollow where I took both dune & shore photos on that first post).
North Truro - map marker across from Pilgrim Lake labeled "Truro/High Head - Surf."