Horn, a brass musical instrument resembling the trumpet. The "French" or hunting horn, out of which has grown the modern orchestral horn, consisted of a long slender tube gracefully curved in several concentric circles and terminating in a bell. The horn has a compass of about four octaves.
Its open tones are harmonies of the natural tone of the tube. Since it has been used in orchestral music a method has been devised of varying its pitch by means of detachable crooks of different lengths, which are added to the tube so as to increase the length of the latter. The pitch can be further modified by means of the "tuning-crooks" or "tuning-slide." The method of producing close tones by placing the hand inside the bell was invented by Hampl of Dresden in 1770. Ventils or valves are now generally used for the rendering of rapid passages.