The large orchestral harp is also called a pedal harp, because it has pedals that are played with the feet. These pedals allow you to change key. There are seven pedals, each one for a different note – for example, a C pedal, D pedal, etc. When the C pedal is moved, all of the C strings on the harp are changed to either natural, sharp, or flat.
The Celtic, or lever, harp does not have pedals, but has sharping levers to change keys. These small levers control one string at a time. A string can be set to natural or sharp, or natural and flat, but not all three.
The advantages of the pedal harp are that one can change keys faster, and play more chromatic music – jazz is playable on a pedal harp, but not realistic on a lever harp. The pedal harp is also built for volume, to be heard over the sound of an orchestra. Disadvantages of the pedal harp include the weight (usually 75 pounds or more) and the expense – $10,000-30,000 and up.
The lever harp is built for beautiful tone, to play beautiful music. Advantages of the lever harp include portability (20-25 pounds in wood for a full sized harp, or 8 to 10 pounds for the same sizes in carbon fiber) and more reasonable price ($2000-$6000). The variety of music playable on a lever harp includes Celtic, classical, sacred, folk, pop, ethnic, and original. There is an enormous amount of music published for lever harp, and more is produced all the time.