four-minute concerto for piano and a one-minute prelude, were found in his sister Nannerl's music book, in the archives of the International Mozarteum Foundation.
They were "in all probability, bordering on certainty" the works of the young Mozart, composed around 1763-1764 when the prodigy was seven or eight years old, the foundation said on Sunday.
The two pieces were performed in front of the media by clavichordist Florian Birsak on Mozart's own fortepiano at the family's old Salzburg residence.
The public however will have to wait until next year to hear them, complete with orchestrations, at the annual Mozart Week on January 22-31 in Salzburg.
Nannerl's music book, which has been in the foundation's archives since 1864, contained 18 pieces, all attributed until now to Mozart's father Leopold or unknown composers.
The two newly discovered works were also written in Leopold's hand.
"But neither the style of composition, nor the hasty correction-laden writing point to Leopold's authorship," Mozarteum researcher Ulrich Leisinger said.
"It is much more likely that Wolfgang Amadeus played the composition on the piano for his father, who then wrote it down for Wolfgang, who was still inexperienced in music writing, and later corrected it," he added.
The two pieces were unusually difficult for piano compositions at the time and their breakneck speed was untypical for Leopold, Leisinger also said.
"This was a young musician running riot in order to show what he was capable of," he noted.
|A pianist performs on two newly discovered pieces by Mozart for the first time in public in a house where he lived, in Salzburg.|
"Moreover, the piece contains real technical mistakes in composition as well as clumsy elements that never would have happened to an old hand like Leopold."
Recordings of the two pieces can be found at www.mozarteum.at -- the website of the foundation which aims to preserve Mozart's heritage and works and organises regular concerts.
The partitions will also be included in a printed version of Nannerl's notebook in the next few months.
Mozart, born in Salzburg in 1756, began composing at the age of five and went on to produce some of the most famous concertos, symphonies and operas of his time, until his death in 1791.
The latest scores are not the only ones to have resurfaced in recent years.
|Mozart's music sheet, which was recently identified as part of a childhood creation by him.|
Last September, a library in Nantes, in western France, unveiled a hitherto unknown music score by Mozart that had lain in its archive undiscovered for over a century. It was authenticated by the Mozarteum.
In 2006, a year filled with celebrations for the 250th anniversary of Austria's favourite son, another piano score extremely likely to be the work of young Wolfgang Amadeus was discovered in Salzburg.
In May of last year, experts also identified three mystery musical scores discovered at Poland's historic Jasna Gora Roman Catholic monastery in southern Poland, as possible Mozart creations.