Today, the Industrial Revolution transforms musical machines. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

The word French horn is a slang term for a long hunting horn that's been bent into a coil. The proper word, in any language, is simply horn. And it traces straight back to the first animal-horns that played only one pitch.

Animal horns had mutated into a huge array of wind instruments by 1600, but most were still straight tubes, flared toward one end. A lot of hunting and military horn-playing was done on horseback, so horns stayed short and high-pitched. Then horn-makers started bending instruments to make them more compact.

In no time, longer horns with richer tones appeared fully coiled. Horns were suddenly being bent about in remarkably complex ways. A French horn is really just a Swiss Alpenhorn. Of course, a 15-foot Alpenhorn will no more fit into an orchestra pit than it will on a horse. So the orchestra brasses took on a wild profusion of forms. Some became real plumbers' nightmares.

Horn players have always used their lips to vary pitches. Players then and now set up different standing waves by changing the set of their mouths. But that alone gives a limited range of pitches. Music, like machinery, underwent a great change during the Industrial Revolution. That Revolution also produced Beethoven and the demand for orchestras with a far greater range of sound. In the decade before Beethoven's death, French horns took on sophisticated valving just as the new steam engines had. Valves let players splice small lengths of tubing into the coils so horns would play naturally in more convenient keys.

By the 20th century you could buy a double horn -- a pair of horns, in different keys, coiled together with a single mouthpiece anda single bell. With one of these, a player is secure in the upper registers while he keeps the nice tone quality of the lower notes.

French horns now come in a thousand variations: single, double, and even triple horns are made in four keys or combinations of keys. Three kinds of valving, many coil arrangements, extra valves, and different bore sizes! Choosing a horn poses a startling combinatorial problem.

Mechanical sophistication was the outcome of the Industrial Revolution, and it touched the whole orchestra. The modern piano emerged, with enormously complex mechanisms and a structure that reflected the new iron bridges.

Today, musical instruments are wed to 20th-century electronics, yet the ideal is the same. The technology of every age has been used to enhance the beauty of natural sounds -- blown animal horns and reeds, resonant cavities, and vibrating strings.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.