The organ has been described, along with the clock, as the most complex of all mechanical instruments developed before the Industrial Revolution. Mozart called it the king of instruments.
The largest concert-hall organ in the United States — all 32 tons of it — recently made its debut at Philadelphia's Kimmel Center for the Performing Arts.
"Millions of people hear the organ every weekend ... in church, but how the thing works does remain kind of mysterious," music commentator Miles Hoffman says.
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