In the 18th century the child prodigy Wolfgang Amadeus Mozart was considered one of nature's wonders. No less astonishing today is the overwhelming popularity of the composer, born in 1756, the son of a Salzburg, Austria violin teacher. "The little man with wig and sword," as the German poet Goethe called 7-year-old Mozart on first seeing him, had by age 9 dazzled the courts of Austria, France and England and turned out 10 sonatas and five symphonies.

The fifth symphony was lost for 216 years. Then in 1980 it mysteriously surfaced in Bavaria and last August received its first U.S. performance, which took place on the White House lawn. Admittedly a slight work, only 11 minutes long and probably composed with help from his father, it nonetheless won a "Wasn't that lovely!" exclamation from Ronald Reagan. Meanwhile, on Broadway, Amadeus, Peter Schaffer's Tony Award-winning play about Mozart, continues to draw SRO audiences. LPs of his works now outnumber those by any other classical composer. No other opera on public TV has equaled the audience of Mozart's Don Giovanni in 1978. His music seems everywhere; even The French Lieutenant's Woman closes to the slow movement of the composer's last piano sonata.

"The prodigy that God has vouchsafed to be born in Salzburg," as papa Leopold Mozart put it, began showing his genius at 3 by climbing up to the clavier keyboard and picking out harmonies. He began taking lessons at 4, and his sister, Maria Anna, a pianist and singer four and a half years his senior, noted, "He learned a minuet in half an hour." By 5, he was improvising little pieces, which his father jotted down. Next, Mozart taught himself to play a half-size violin, and Leopold decided it was time to take the brother-and-sister act on the road.

In 1762 a tour meant the royal and princely courts, and Wolfgang and Maria Anna soon were in Vienna's Schönbrunn Palace, where the Austrian empress, Maria Theresa, took such a liking to the tiny musician that he bounded onto her lap to be kissed. Another conquest was 7-year-old Marie Antoinette, the ill-fated future Queen of France, who helped Wolfgang to his feet after he slipped on the palace floor. "You are very good," he thanked her, "and when I grow up I shall marry you."

At Versailles he was summoned by France's Louis XV to the royal table, where Queen Marie spooned food into his mouth as she translated his prattlings from German into French for the King. (Mozart had less luck with Madame de Pompadour, who refused to let him give her a peck on the cheek, sending him into a snit.)

London was the final triumph. The Mozarts were invited to the King's apartment in Buckingham House, as it was then called, where Wolfgang overwhelmed music-loving George III, 27, by playing at sight pieces by Handel and Johann Christian Bach. He followed that by a show of virtuoso improvisation. "The welcome we have received here exceeds all others," exulted Leopold. At a public concert Wolfgang and his sister earned 100 guineas (about $51,000 in today's currency) for playing a concerto for two harpsichords. Leopold made his son available every day from noon until 3 p.m. for skeptics willing to pay to test the child's skills.

By the time Mozart sailed home from Dover on Aug. 1,1765, he was well launched on a composing career that would end at age 35, when he died penniless of kidney disease. His spendthrift ways and prickly manner combined with the backbiting of contemporaries to blight a career so brilliantly begun. However, more than 600 works survive, and a century and a half later George Bernard Shaw noted that Mozart, in his opera The Magic Flute, had written the only song, In diesen heil'gen Hallen (Within this hallowed dwelling), that would sound right coming from the mouth of God.