Of all the things we human beings have ever made for ourselves, string instruments are among the most highly valued. Great performers on string instruments-whether the violin and cello of western classical music, the sitar and sarod of Indian traditions, or the electric guitar-are treated as stars. Exceptional instruments can sell for enormous prices. Yet the basic principle is very simple: a string instrument is a box with strings stretched across it. You could make one yourself-only don't expect an enormous price for it, because an immense amount of knowledge and experience goes into the real craft of making string instruments.

For instance, special woods are carefully chosen and carved to make the box, which in the case of western classical instruments has a figure-of-eight shape with a handle. This is the fingerboard, on which the musician's fingers move up and down to change the length of string that can vibrate, and so to change the note. The note will depend not only on the string's length but also on how tightly it is stretched, which is why you see string players tightening or loosening the strings in order to tune their instruments-that is, to make the strings give the notes they should. A string by itself would not make very much sound, which is why the box is there, to resonate and so amplify the sound, at the same time-this is the craft-making it richer, warmer, sweeter.

String instruments can be plucked, as a guitar is, or else played with a bow, so called because it's like a bow used to shoot arrows: a gently curved piece of wood whose ends are joined by something tough but flexible-hairs from a horse's tail in the case of instruments. The four kinds of string instrument most often used in western classical music are usually bowed. They differ in size and therefore in the sound they make. The violin, smallest and with the shortest strings, is highest, playing in the register of a woman's singing voice (and higher). Next comes the viola, then the cello, and finally the double bass.