Pictorial evidence of harps appears as early as 4000 BCE. Bow- and spoon-shaped harps with six to 12 strings were widely used in Egypt around 3000 BCE.
By the 14th century, the Western European harp added a string arm and a column to the soundbox of earlier models. In the 1720s, Jacob Hochbrucker introduced a mechanism for changing the pitch of strings using foot-operated pedals.
The modern pedal harp is based on the double-action harp patented by Sebastien Erard in 1810. Double-action pedal mechanisms allow any string to be played in its flat, natural or sharp position.
The "folk harps" used by Celtic harpists are lever harps, which use levers positioned at the top of the strings to change the string pitch. This type of harp allows two notes per string.
Harmonically complex music requires a pedal harp, but Irish folk music and Renaissance music can be played using the lighter, more portable lever harp.