Two Ph.D. candidates at MIT have invented The Sound of Touch, a digital instrument that texturizes sound. It works like this: you use a microphone built in to the wand-like instrument to record a sound, then you brush the tip of the wand across a surface. A processor translates the shape of that surface into an effect applied to the sound. Sandpaper would gives your sample a gritty sound, silk a satiny smoothness.