The qanun, a Middle Eastern instrument, is a plucked zither chordophone. Its name derives from the Greek word canon and means "rule" or "law." Played horizontally on one's lap or on a special stand, it looks like a thin, trapezoidal box. There are 81 strings stretched across it in groups of three (all tuned to the same note in different octaves), making 21 ready to pluck chords. The plucking is done either by purely by hand or two plectra attached to the pointer finger of each hand. Tiny levers are placed under the stringers on the left side that can change the tuning in the middle of a song (not unlike a whammy bar). It is known for being able to play scales faster than any other Arabic instrument.
The qanun descended from the Egyptian harp, another plucked zither chordophone. Supposed, it was created by the Arab philosopher, Ibn Al-Farabi. Whether the qanun played a role in the evolution of Western zithers is in dispute. Some ethnomusicologists argue that qawanin (the plural form of qanun) were among the many instruments brought back and acculturated in Europe by the Crusades around 12th century. If so, the it's possible that hammered dulcimers, harpsichords and modern pianos are all descendants of the qanun. Most of these other trapezoidal instruments just replace the plectra with hammers and become mechanized with keys.
The qanun isn't restricted to Arab music today as Turkish, Persian and Greek traditional music are played on it. Current players of the qanun include composers of these types of music, Middle Eastern ensembles and students of ethnomusicology.
Sources:
World music class
http://www.music.ucsb.edu/mee/instruments.html
http://almashriq.hiof.no/lebanon/700/780/fairuz/legend/instruments.html#qanun
http://islamicchants.hispeed.com/html/17-taqsim.htm