WASHINGTON - Practice, practice, practice - a dreaded refrain heard by millions of children who toil over an instrument that began as entertainment for the elite and became a 20th century symbol of prosperity and gentility for America's middle class: the piano.
Jazz pianist Dave Brubeck, who will be 80 this year, said some of the old pianos in a yearlong show opening Thursday at the National Museum of American History were part of his youth.
''I was raised on a cattle ranch,'' he recalled at a news conference Wednesday, ''and you'd be surprised how many people had pianos. A neighbor had a square piano I played when I was a kid, and when I go back, it's still there.''
His first music teacher was his mother. She had studied with Dame Myra Hess - the classical pianist known for her lunchtime performances in London's National Gallery when the bombardments of World War II had closed all the concert halls.
The first documented appearance of the piano was in Italy about 300 years ago.
The show includes one of the three surviving instruments made by Bartolomeo Cristofori, who lived from 1655 to 1732. He invented ''a kind of harpsichord ... with some hammers that play the soft and the loud,'' according to an inventory from the year 1700 made for the Medici family that ruled Florence.
It was the soft (piano in Italian) and the loud (forte) that gave the instrument its name ''pianoforte,'' later shortened to piano. The hammers that strike the strings gave composers a whole new range of possibilities over the harpsichord that just plucks the strings with quills.
The 25 pianos in the show include square pianos, a portable upright, a ''giraffe'' piano - a grand standing on its head, a ''sewing table'' piano with scissors and a mirror, a miniature said to have been made for ''General Tom Thumb,'' a P.T. Barnum attraction, and Liberace's rhinestone-studded grand.
And there's the upright that belonged to Irving Berlin, who composed largely on just the black notes. It has a trick lever for transposing from one key to another.
''The black keys are right there under your fingers,'' he said. ''The key of C is for people who study music.''
Musicians consider the key of C the most elementary.
EDITOR'S NOTE - ''Piano 300 - Three Centuries of People and Pianos'' will be at the S. Dillon Ripley Center, next to the Smithsonian Institution's ''castle'' headquarters, through March 4, 2001. Admission is free.