Bagpipes are a class of musical instrument, aerophones, using enclosed reeds fed from a constant reservoir of air in the form of a bag. Though the Scottish Great Highland bagpipes have the greatest visibility in the English-speaking world, bagpipes have been played for centuries (and continue to be played) throughout large parts of Europe, Turkey, the Caucasus, around the Persian Gulf, Northern Africa and North America. The term "bagpipe" is equally correct in the singular or plural, although in the English language, pipers most commonly talk of "the pipes", "a set of pipes" or "a stand of pipes".