The qanun is a descendent of the old Egyptian harp and has played an integral part in Arabic music since the tenth century. Its Arabic name means 'rule' or 'law.', which itself derives form the Greek word “canon”. The qanun was introduced to Europe by the 12th century, where it became known during the 14th to the 16th C as a psaltery or zither.

The qanun is trapezoidal which 26 courses of strings which are stretched in groups of three. The instrument is placed flat on the knees or table; the strings are plucked with the finger or with two plectra, one plectrum attached to the forefinger of each hand. More than any other instrument in Arabic music, the qanun is suitable for the display of virtuosity.

The strings are tuned to the basic notes of a given scale and the pitch is raised or lowered by stopping the strings with a series of metal levers. The qanun player can play many types of intervals.

This traditional Arabic instrument has been replaced by the less complex piano.

Reference:
al-hakawati http://al-hakawati.net/Art/ArtDetails/63/القانون.