The harp is one of the oldest string-percussion instruments, found in various forms all over the world.
(Public domain image from Websters Dictionary 1911 Full size image)
It may have been invented when people found that the sound of a plucked bow string sounded nice, and added extra strings to the bow. The harp is mentioned in the Bible, ancient epics, even in Egyptian wall paintings. Today, there are two main types of modern harps: folk and concert. Different kinds of folk harps are found all over the world.
Harps are triangular and have nylon, gut, wire, and/or copper wound nylon strings. Harpists can tell what notes they are playing because all F strings are black and all C strings are red or orange. The harp is rested in between the knees of the harpist and along their right shoulder. The first four fingers on each hand are used to pluck the strings (not the pinky fingers). Plucking louder and softer creates dynamics. Depending on finger position, different sounds can be produced: a "fleshy" pluck (near the middle of the first finger joint) will make a warm tone, and a pluck near the end of the finger will make a loud, bright sound.
There are two main methods of harp technique: the French (or Grandjany) method and the Salzedo method. Neither one has a definite majority among harpists, but the issue of which is better is a source of friction and debate. The distinguishing features of the Salzedo method are the encouragement of expressive gestures, elbows stay parallel to the ground, wrists are comparatively stiff, and the neither arm ever touches the soundboard. The French method advocates lowered elbows, fluid wrists, and the right arm resting lightly on the soundboard. In both methods, the shoulders, neck, and back are relaxed. Some harpists combine the two methods into their own version that works best for them.
The pedal harp has six and a half octaves (47 strings), weighs about 70 pounds, and is approximately 6 feet high and 4 feet wide at the widest. It uses pedals to change the pitches of the strings. There are seven pedals, one for each note. When a pedal is raised, all the strings of that note are lengthened a half-step, resulting in a flat. When it is lowered, the strings are shortened to make a sharp. This mechanism is called the double-action pedal system, invented by Sebastian Erard in 1810.
The folk harp ranges in size from two octaves to about six octaves, and uses levers to change the pitches. At the top of each string is a lever, and when it is depressed, its pitch is raised a half-step, resulting in a sharp if the string was in natural.
Many parts of the world have their own type of harp. In South America, the mariachi, Paraguayan, and Venezuelan harps are similar to Spanish harps: wide on the bottom and narrow at the top with very light string tension. In Asia, the koto is a form of lyre, a close relative of the harp. Africa has the kora. Ireland has triple-strung harps and metal-strung harps (played with the fingernails). Spain has the chromatic harp, with two crossing rows of strings. Ancient Greece had lyres, similar to harps but not triangular.
The harp is sparingly used in most classical music, usually for special effects such as the glissando, arpeggios, and bisbligliando. Italian and German opera uses harp for romantic arias and dances, an example of which is Musetta's Waltz from La Boheme. French composers such as Claude Debussy and Maurice Ravel composed harp concertos and chamber music widely played today. Henriette Renie and Marcel Grandjany have composed many lesser-known solo pieces and chamber music. Modern composers use a lot of harp because the pedals on a concert harp allow many sorts of non-diatonic scales and strange accidentals to be played (of course they don't care if it is practically impossible to move the number of pedals they want! :))
Lyon and Healy has developed an electric harp. It is a concert harp, but with pickups at the bottom of each string and an amplifier. The electric harp weighs a lot more than an acoustic harp, but looks the same.
External link: http://www.tns.lcs.mit.edu/harp/ (a list of other good links)