On the subject of the physical value of sound, this is another interesting example. Kanta Horio created Particle, an instrument containing nine electromagnets and broken paper-clips. By controlling the current for each magnet separately the instrument creates interesting patterns.
What I particularly like about Particle is how it physically shows you how the somewhat abstract sounds are created. This makes it more interesting to watch than similar sounds being produced and processed by a computer. The performance lacks complexity though. By adding various other layers of sound a more interesting composition could be created, with sounds from Particle as an ongoing supporting element, rustling in the background.