At ten o'clock on Friday morning, Vienna's huge and venerable Burgtheater was packed.
By Bethany Bell
BBC News, Vienna
The pianist Rudolf Buchbinder was performing a selection of Mozart's piano works, interspersed with readings from the composer's letters.
Children are being educated about the life of Mozart
The event is just one of hundreds taking place in Vienna and Salzburg, to mark the birthday of a man once described by Goethe as a "miracle that cannot be explained".
Mozart is still a superstar, 250 years after his birth.
Standing in the marble vestibule of the Burgtheater after the concert, Clementine, a teacher from the province of Lower Austria, said she was spending the whole day at the Vienna Mozart celebrations.
"He was a genius - and I think his music has got everything. It's light, but it can be heavy as well. It's exciting and it's full of emotion. It's just wonderful."
Out in the streets of Vienna, Mozart's face is everywhere, advertising exhibitions, concerts and guided tours. One tongue-in cheek-poster shows the composer rolling his eyes in disbelief at all the fuss.
But neither the hype nor the freezing temperatures seem to deter determined Mozart fans.
Standing in a queue outside Vienna's new Mozart museum, stamping his feet in the cold, Hirokomi Ira said that he had travelled all the way from Osaka in Japan to be in Austria on the 27 January.
"I wanted to say Happy Birthday Mozart! I love his music," he said.
Tour guides - in both Vienna and Salzburg - are having a field day, as thousands of tourists converge on the Mozart sites.
"For me it's something fantastic, because once again everyone is reminded that Mozart was here," said Vienna tour guide Brigitte Roth.
The Vienna Boys Choir will be performing Mozart
"But it's all is a bit exaggerated - so much is going on."
Salzburg, the city of Mozart's birth, is also running a star-studded series of concerts and cultural events, including performances by the Vienna Philharmonic Orchestra.
But in its narrow cobbled streets the full impact of Mozart marketing comes to the fore.
Souvenir shops are stuffed with memorabilia, from Mozart perfume to Mozart sausage.
One local dairy has even developed a Mozart yoghurt, flavoured with chocolate and marzipan.
Austrian President Heinz Fischer told the BBC that there is a danger of overkill throughout the Mozart anniversary year.
"We must be careful that after three or four months, people in Austria might not be able to stand to listen to Mozart any more," he said.
"There is a danger of very strong commercialisation - but Mozart definitely can survive it. He is a figure of world cultural heritage and he will survive the centuries."
While some Salzburgers say they will be boycotting the centre of town until next year, most Austrians appear to be enjoying the celebrations.
"Do you know, I've just bought a new Mozart CD, Symphony Number 81, which is unknown to me," said Christiane, a young Viennese woman.
"I'm planning to go to a lot of the events over the next few days and tonight we are having a family reunion and we will play Mozart."
"Mozart's music is really enriching - for every one of us."