https://silentlistening.files.wordpress.com/2008/05/sea_organ.mp3″

There is a small group of musical instruments that operate without human interaction, the aeolian harp or wind chimes are commonly known as such unintentional sound producers.The Sea organ based in Zadar, Croatia, is another example: a system of polyethylene tubes situated underneath white marble steps are “played” by the incoming waves of the sea shore and produce organ-like tones as in the above sound example. The inventors tried to reflect the local urban musical tradition, therefore the 35 pipes of the sea organ were tuned according to the “autochthonous diatonic major scale”. More details on the construction can be found here. Similar devices are located in San Francisco, California (wave organ) and in Blackpool, UK (Blackpool High Tide Organ).