This piece of music became very popular, and the Vatican did not want anyone else to perform it. No one was allowed to take the music away from the chapel or make copies of it. The Vatican called for excommunication of anyone trying to make a copy. However by 1770 there were three known copies of the music. One of these was given to the Emperor Leopold I by the pope. Wolfgang Amadeus Mozart visited the Sistine Chapel during a tour of Europe with his father in 1770. He was just 14 years old, but heard the piece and wrote all the music out from memory later the same day. A second visit enabled him to check that he had it written correctly. It is believed that Mozart's copy of the music was sent to England where it was published by Dr Charles Burney. It would be assumed that Mozart would have written the improvisations in his copy. Burney's version lacks the improvisations, so it possible that he removed them, and destroyed Mozart's copy to avoid trouble with the church. There were no copyright laws in those days, so there was nothing that the Vatican could do about it.