If it wasn't for Mozart, this piece would have been forgotten forever

The incredible story of how Mozart came to copy down Allegri's Miserere, note for note, after hearing it just once in 1770.

You might have first heard Allegri's Miserere at the movies – in Chariots of Fire. Or in Angela's Ashes. Or even Face/Off.

Once it's heard though, never forgotten. That soaring high C, mortifying for the boy treble who has to reach it, makes it one of the most sublime pieces of choral music ever.

But the piece was once closely guarded, only ever sung during the days of Easter within in the hallowed confines of St. Peter's Rome – and never published for performance anywhere else.

In 1770, who should arrive at the Vatican for Easter but 14-year old Wolfgang Amadeus Mozart? The city was captivating. He was overawed by St Peter’s, but perhaps unsurprisingly, the greatest impression made on him by that piece of music.

When he returned to his lodgings — where he had to share a bed with his dad and, was getting no sleep at all – Mozart wrote the entire piece out from memory, perfectly. He went back to St Peter’s to hear the work again, probably the same week, to compare his own score with the sung version.

And that, so the story goes, is how we know and love Allegri's Miserere to this day.