David Bowen is an artist who uses data. He has used data to point an installation of 50 twigs in unison towards the largest piece of space junk currently overhead. He used data to allow the flight of flies to control, aim and shot a revolver. He is not a musician, yet he used MIDI Manufacturer Association member Ableton's Max MSP software to create a Cloud Piano, a piano played by clouds.
in this installation, Bowen used Max MSP and mapped Video to MIDI so that whenever a cloud passes over a note on the keyboard, the MIDI controller robotic arms presses the keys on an acoustic piano for the duration the clouds are over them. If there's more white than blue detected, the key is pressed.
He went further and mapped multiple different video attributes to MIDI parameters. Tempo and rhythm are naturally related to how quickly the clouds are moving. Dynamics are controlled by how brightness, the more white in the video, the louder the sounds are played by generating higher MIDI velocities. Even the overall feeling of the music is based on the video input. Clouds moving in one direction are processed to have a major feel, Clouds moving the in opposite direction are processed with more minor tonalities.
Of course, this installation wouldn't work well in Southern California. There would be too many days when there was no sound at all because there were no clouds in the sky. It might not work well in Seattle in the winter when skies are overcast for months on end. But we never cease to be amazed at the creative ways artist come up with to use MIDI.
Here is a Youtube video from Great Big Story "That's Amazing" about how the installation was put together.