Lagniappe - How to tune an orchestra

If you've ever been to a classical concert, you've probably gotten to listen to the orchestra tune up in the final few minutes before the concert starts.  Ever wondered how that works?

Here's what the pre-concert tune-up looks like:

The orchestra is led in tuning by the oboe.  Why the oboe?  Simple.  The oboe carries over the crowd better than any other instrument.  

The oboist tunes her instrument offstage, before the audience starts shuffling in and before the members of the orchestra start taking their places onstage.  Typically, tuning is done with an electronic meter, although it can also be done with a tuning fork or pitch pipe.  The standard for most orchestras is that the A above middle C is exactly 440 Hertz (vibrations per second).  439 Hz will not do, neither will 441.  The oboist adjusts her instrument until an A played on her oboe matches the A-440 sounded on her meter.

When the concertmaster (head 1st violin) comes out on stage, he directs the oboist to play her A.  All the horns and woodwinds tune to her A.  The horns adjust their tuning slides, and the woodwinds tune by adjusting the sections of the barrels of their instruments.  

Once the horns and woodwinds have finished, the oboist plays her A again, and the cellos and string basses tune to it.  Violins, violas, cellos, and basses are tuned by turning tuning pegs on the neck of the instrument.  The cellos and basses tune their A strings first, then tune their other three strings using the A string as a reference.

Finally the oboist plays her A a third time, and now the violins and violas tune, in the same manner as the cellos and basses.

Now that everybody's in tune, the concert can start.  But only when the conductor is good and ready!