The 80-page manuscript, a transcription of the composer's Grosse Fuge for piano duet, was found in the archives of a religious school in Philadelphia. According to Stephen Roe, head of Sotheby's manuscript department, the manuscript had never been seen by scholars.
It will go on sale at Sotheby's in London. The estimated price is well over Ô£1 million. The manuscript will be on display at Sotheby's in New York November 16-19.
The manuscript, which transformed the 1826 string quartet into a piano duet, was written well after Beethoven went deaf. It is not the final version of the work; the annotations, deletions, and corrections are likely to provide a great deal of insight into the composer's thought processes and working methods.
This is not the first time the school, the Palmer Theological Seminary, has found a rare document in its archives. In 1990, a Mozart manuscript was discovered there.