The pedal harp (also known as the concert harp) is a large and technically modern harp, designed primarily for art music and may be played either solo, as part of a chamber ensemble, or in an orchestra.

It typically has a range of six and a half octaves (47 strings), weighs about 36 kilograms (80 lb), is about 1.85 metres (6 ft 1 in) high, has a depth of 1 metre (3 ft 3 in), and is 55 centimetres (1 ft 10 in) wide at the bass end of the soundboard.

The role of the pedals in this type of harp is to alter the pitch of the strings. The pedal harp can easily play works written in any key. This is particularly important in the harmonically complex music of the Romantic period and later 20th-century classical music. Nonetheless, the two lowest strings are not affected by the pedal mechanism. They must be tuned manually in advance for the whole piece (or section of a piece).

More Info: en.wikipedia.org