The Earth Harp
The group Mass Ensemble http://www.massensemble.com/ just finished a four-day stint at the Lexington (KY) Idea Festival http://www.ideafestival.com/. I saw three of their public outdoor performances that included the use of their long-string installation they call the Earth Harp.
The strings are all pulled tight to roughly 30 pounds tension, but since they are played using the longitudinal standing waves, the tension is less important than the length, which they have predetermined mathematically and attached small wooden blocks at the appropriate place on the length of the string. (E.g., middle-C is 42 feet).
The far end of the strings were attached to a wall at the top level of a parking structure across the park, which was roughly 150 feet from the bridge.
The harp was set up for four days and never required further tuning. The blocks attached along the length of the strings tend to dampen a lot of the normal side-to-side oscillation, so there was no discernible aeolian effect to the wires, even being hung in a fairly good breeze. (I felt this was somewhat unfortunate.)
The ensemble consisted of Earth Harp, cello, French horn, bass/guitar/percussionist, drummer (traps), and two female dancers.
One of the more interesting instruments they played was the "drumbrella". This was a bunch (maybe 20 or
so) of standard Remo hand drums that were attached together into an array that could be carried from the back by a central tubular handle. The whole assembly was held together by lots of C-clamps. At one point one of the performers picked it up and started spinning it from the back while three others drummed on it with sticks.