It’s called the Weather Warlock and is the creation of a company called Quintronics, the brainchild of a New Orleans musician named Quintron.
According to Slate, “it works when sensors detect changes in sunlight, wind, rain, and temperature. Copper wires then carry that information via a water-proof casing to the synth that sits, for now, in the living room of Quintron’s home new New Orleans’ 9th Ward.”
Okay, so what kind of music does the weather compose? It depends on Mother Nature’s mood, really. There’s a live stream available 24/7 here.