Croatia

You can listen to a concert played by the waves on the sea organ here.

An excerpt from the article 51 facts about Croatia
They are located near the new port in Zadar. The coast here has the shape of a wide staircase, seventy meters long, sloping down to the sea, in which holes are carved. Thanks to them, you can hear sounds resembling melodies played on bottles filled with water. Under the stairs are hidden 35 pipes of different diameters and lengths. They have been selected and arranged so that the waves hitting them create sounds of different tones. This sea music is unique because the organ sounds depend on whether the sea is calm or rough and how the wind blows.