As you probably don't know, Lauren and I will hopefully be using water surfaces as music controllers live at the Tyndall concert next Thursday. The concept for this comes from a yearning to touch sound.
The idea is pretty damn simple- a laser beam from one of those annoying pen pointers is projected diagonally through a glass vase containing some water, so that it hits the surface and also comes out on the other side.
A basic receiver directly translates movement of the laser (via changes in the water surface) to a wave that can be read on an audio line on on the computer.
The good aspect of this is that the state of the receiver can be read as quickly as audio (...it is audio...). However, the wave does not represent any discrete amounts of energy or steps or whatever, since it represents any particular energy state of the laser (or the receiver) as a fixed, static voltage (unchanging) ie. direct current, which analog to digital audio converters do not seem to like.
So what the wave is showing is the fact that the water is surface is moving in some way- it is showing it is changing, not exactly how much change happens from here to there. At least that's the way it works in my head or something.
This wave is then used to directly modulate audio (like a sine wave or something) and is also translated into data for controlling delay time and feedback values in an asymetric feedback network as well as sine wave frequency. Data is also crossed over from one player to another.
Anyways- this is just the beginning. There's lots of room for development for this idea, I suppose.