Background
A harp is an instrument with one or more strings connected to a perpendicular resonator. Harps have been played around the world for thousands of years, and in that time many different styles have been invented. The oldest and simplest harp is the bow harp. It is a one string bow with a small gourd as a resonator at the bottom. The gourd picks up and amplifies the vibration of the string when it is plucked, making the harp more audible. More modern designs can use more than 40 strings, and have a stable, three-cornered structure to support the tension of all those strings. The basic idea, however, is still the same.
How Harps Work
Harps have a row of tuning pegs on the top and a box-like resonator on the bottom. Strings are stretched between the tuning pegs and the resonator, and adjusted until the harp is in tune. Most harps have a diatonic tuning, using 7 notes in each octave to get a complete major scale. Some harps are chromatically tuned with two rows of strings side by side. The row with the diatonic strings is like the white keys on the piano. The second, chromatic row is like the black keys. When the player plucks a string, the vibration is passed on to the resonator, which amplifies and projects it. The harpist can choose to pluck the strings with the pad of his finger to make a warm, mellow tone, or to use the tip to make a sharper sound.
Concert Harps
Concert harps are normal diatonic harps with a twist: they have seven pedals to raise and lower the pitches of the strings. Each pedal controls one note in every octave. So, for example, one pedal would control all of the A notes. Each pedal has pegs which can be used to raise or lower the note half a step. Pressing on a pedal causes two pegs at the top of the harp to pinch the string. This shortens the length of the string, raising the tone. These pedals allow a harpist to play fully chromatic music.
