Salzburg, Austria ? The huge musical puzzle that is Mozart is about to be expanded by two potentially important pieces.

More than two centuries after his death, two additional works have recently been identified as being composed by the Austrian master. While the pieces might have been played before, Sunday will be the first time they will be performed as compositions of the popular prodigy.

The venue is Salzburg, Amadeus’ birthplace and the city that nurtured his early musical career. The International Mozarteum Foundation will officially present the piano pieces at a hotly awaited event that will feature a live performance by Austrian pianist Florian Birsak.

Officials, protecting the works like state secrets after officially announcing their discovery last week, have said only that they were created by a young Mozart and are contained in a manuscript owned by the Mozarteum for more than 100 years.

“These are two substantial pieces of piano music, composed before Mozart’s 10th birthday,” Ulrich Leisinger, the Mozarteum’s head of research, said in an e-mail to The Associated Press.

They were identified as part of a larger investigation of the foundation’s Mozart-related materials that include letters and documents, but also more than a hundred music manuscripts — some in the hand of the composer, others transcribed by contemporaries.

The foundation, established in 1880 and a prime source for Mozart-related matters, seeks to preserve the composer’s heritage and find new approaches for analyzing him.

Posthumous discoveries of Mozart pieces are rare — but not unheard of.

In September, Leisinger announced that a French library had found another previously unknown piece of music handwritten by Mozart.

That work, described as the preliminary draft of a musical composition, was found in Nantes in western France as library staff members were going through its archives. Leisinger says the library contacted his foundation for help authenticating the work.

There have been up to 10 Mozart discoveries of such importance over the past 50 years, Leisinger said at the time.

Still, experts are fascinated by news of the most recently announced find.

The Juilliard School’s L. Michael Griffel called it “very exciting” and a “thrill for intellectuals.”

“It’s always so impressive when a new piece of Mozart is discovered because it adds to the total picture that we have of him and of his development as a composer,” said Griffel, chair of the renowned institution’s music history department.