Many people when thinking of harps think first of the large, ornate classical pedal harps seen on stage with symphony orchestras. Classical, or pedal, harps use pedals instead of levers to change keys.
The pedal mechanism is fairly complex: pushing the pedals moves discs located at the top of the harp which shorten (and thereby sharpen) the strings. In addition to its deep, rich tone, the advantage of a pedal harp is that you can play accidentals easily and quickly, as well as being able to change keys quickly.
Lever, or folk, harps are so called because the mechanisms used to change keys are levers that are attached to the harp and push against the strings to make them shorter and thus sharpen the string. The advantage of lever harps is that they are lighter and more portable and can come in many sizes, from tiny lap harps to beautiful full-size floor harps like my Prelude.
A Brief Introduction to the Harp … American Harp Society
The History of the Harp … International Harp Museum
A Primer on Harp Maintenance … Mike Lewis at HarpTech
The harp at Nature’s advent strung … John Greenleaf Whittier
“Send forth your light and your truth, let them guide me; let them bring me to your holy mountain, to the place where you dwell. Then will I go to the altar of God, to God, my joy and my delight. I will praise you with the harp, O God, my God.” (Psalm 43.3-4)