http://www.news.cornell.edu/releases/nov03/nemsguitar.ws.html

A more portable guitar: “Its strings are really silicon bars, 150 by 200 nanometers in cross-section and ranging from 6 to 12 micrometers in length (a micrometer is one-millionth of a meter; a nanometer is a billionth of a meter, the length of three silicon atoms in a row). The strings vibrate at frequencies 17 octaves higher than those of a real guitar, or about 130,000 times higher.”