Algorithm to complete Beethoven's unfinished symphony

Musician and software developers have created an algorithm that will take over where Beethoven left off, and finish the composer's uncompleted tenth symphony, Germany's Frankfurter Allgemeine Sonntagszeitung (FAZ) reported Sunday.

However, the developers told FAZ they are not certain what the final composition will sound like.

"The algorithm is unpredictable, and it surprises us every day," said lead developer Matthias Röder. "It is like a small child discovering the world of Beethoven."

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The idea and funding for the project were provided by German telecommunications company Deutsche Telekom for Beethoven Year 2020, celebrating the composer's 250th birthday.

The algorithm-composed symphony will be performed in April by the Bonn Beethoven Orchestra. The developers still have some work to do. 

Röder, director of the Austrian music technology hub Karajan Institute, has led an international team of musicologists, composers and IT specialists since summer 2019 to develop an algorithm that thinks like Beethoven.

How it works

The developers told FAZ that the algorithm is based on language recognition technology. It works by a programmer feeding bits of Beethoven's music into the software for the algorithm to recognize.

The program then plays back its improvised interpretation. The programmer provides input for what musical styles work with a Beethoven-like piece. The process is repeated until the algorithm gets enough input to compose its own kind of Beethoven.

Röder told FAZ the first few tests in summer were challenging. After a few bars, the program was supposed to take over and improvise, but it ended up playing endless loop of sounds

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"It sounded more like Stravinsky than Beethoven," said Röder, adding that now the program has an idea of what Beethoven is supposed to sound like. The algorithm also needs to predict the blend of surprise and consistency that creates rich compositions.

During a test with music experts in November at the Beethoven House in Bonn, a few bars of the tenth were played, until the algorithm took over for over a minute with an improvised interpretation.

"No machine has ever made it this long before," said music technologist Röder. "This is unparalleled."

The developers told FAZ that they consider the program a success if a listener can't distinguish between original Beethoven and the algorithmic creation.

Why is the 10th unfinished?

The current version of Beethoven's 10th in E flat major is a hypothetical work that was put together by British musicologist Barry Cooper from a few fragmented sketches Beethoven composed before his death in 1827.

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Beethoven had worked on pieces of a new symphony in the early 1820s and the last known sketch dates from 1825, according to an essay by Cooper.

Cooper's version was first performed in 1988 by the London Philharmonic Orchestra.