From Some Amazing Facts:
The Singing Tree. The Wind blowing makes music : Lancashire – England — with Arsy.
Ralphie: “I wish there was sound to go with it.”
Explanation by Twila Skinner –
Designed by architects Mike Tonkin and Anna Liu of Tonkin Liu, the Singing Ringing Tree is a 3 metre tall construction comprising pipes of galvanised steel which harness the energy of the wind to produce a slightly discordant and penetrating choral sound covering a range of several octaves.
Some of the pipes are primarily structural and aesthetic elements, while others have been cut across their width enabling the sound. The harmonic and singing qualities of the tree were produced by tuning the pipes according to their length by adding holes to the underside of each.