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What Do Leap Year and Tuning A Piano Have in Common?

 Monday, February 29, 2016

By Jean Newton, Executive Director

It takes 365.25 days for the earth to revolve around the sun, but our calendar only has 365 days, so every four years we get an extra day. We’ve “scheduled” this day on February 29th and call it “Leap Year.” But imagine if we decided instead to divide up that extra day, and give a little piece of it to some or all of the other days in the calendar.

On a piano, there’s a difference in pitch of .25 semitone between 12 perfectly tuned fifths and 8 perfect octaves. A semitone is one half-step, or two consecutive notes such as C/C#. Without going into the mathematics of piano tuning, if you try to play a piano with all perfectly tuned intervals, it will sound AWFUL!!

So, piano tuners have to take that extra .25 semitone and divide it up among all the other intervals. We call this “tempering” the tuning. In fact, the only perfectly tuned intervals on a piano are the octave and the fifth; all the others are a tiny bit imperfect, so that the piano will sound beautifully in tune.

There are many different ways of “tempering” a piano. Today, we use “equal temperament” – meaning that all the intervals, except for octaves and fifths, are “imperfect” by the same amount. But in previous centuries, keyboard instruments were tuned using “well temperaments” – meaning that the intervals were not all tuned the same. Nearly every piano student plays pieces from J.S. Bach’s “Well Tempered Klavier,” which includes a prelude and fugue in every single key. Bach was demonstrating that a good temperament would allow all the intervals and harmonies in each key signature to sound beautiful!

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