When the world-famous composer Ludwig van Beethoven died in 1827, he left behind nine symphonies - and small parts of a tenth. No one has been able to imagine what the finished piece would sound like - until now.
To celebrate the composer's 250th anniversary, a team of music researchers and programmers together with German telecommunications company Deutsche Telekom have tried to complete the work with the help of an artificial intelligence, AI.
Hear how the result sounds in the clip above.