Displayed to the public at the Palmer Theological Seminary for just one afternoon yesterday, the 80-page manuscript, dated 1826, is a seminal find for scholars of Beethoven and classical music. Written in brown and black ink, it is crammed with annotations and corrections and thus will give new insight into the creative patterns of the composer, who at the time was already stone deaf and only months from death.
"This is an amazing find," said Stephen Roe, head of the manuscript department at Sotheby's.
"The manuscript was only known from a brief description in a catalogue in 1890 and it has never before been seen or described by Beethoven scholars." When put under the hammer, the score, composed for four-handed piano, is expected to fetch up to $2.6m (£1.5m).
Heather Carbo, the librarian, was cleaning out cabinets at the evangelical school one afternoon in July. Suddenly, she spotted the dusty manuscript in a paper and board cover sitting on a low shelf.
At first, she hardly knew it would soon be setting the whole musicological community atwitter. "It was just sitting on that lower shelf," she told The New York Times yesterday. "I was just in a state of shock." Another public viewing is set for mid-November at Sotheby's in Manhattan before the manuscript is moved to London for the auction on 1 December.
Experts say it will be the most important Beethoven score to surface for sale in living memory.
The score is a work in progress. Widely recognised as one of Beethoven's most monumental compositions, the Grosse Fuge was originally written for a string quartet. The manuscript is the only known example of a major Beethoven work transcribed by the composer for the piano. It is also one of only a very few he completed at all for duet piano.
Especially revealing are all the corrections and scribbles illustrating the composer's perfectionism as he strived to get the piece exactly to his liking. Discarded fragments of music are scratched out, sometimes marked "aus" (out). Some of the cross-outs are so determined, Beethoven's pen has penetrated the paper. At one point, the composer has overlaid a new page on to a page of discarded bars with red wax.
Richard Kramer, a musicologist with the City University of New York, told the Times: "What this document gives us is rare insight into the imponderable process of decision making by which this most complex of quartet movements is made over into a work for piano four-hands."
The school has experienced such excitement before. In 1990, its workers stumbled upon a Mozart score in its archives. "At that time we called it the Mozart miracle. It seems appropriate that this time we are thankful for the Beethoven blessing," said its president, Wallace Charles Smith.
According to the Times, the original source of the seminary's treasures was probably a Cincinnati industrialist, William Howard Deane, who was a musical enthusiast and collector.
In 1952, his daughter made a gift to the seminary, which included the Mozart manuscripts. It was rumoured for years that an important Beethoven score was also lying around the school somewhere.
It is likely the manuscript represents a labour of love by Beethoven, whose original version ofGrosse Fuge, written for strings, was panned by critics and not much cheered by audiences.
His publisher commissioned somebody else to re-craft the work for piano. But the piece was so complex that Beethoven may have felt that only he could do the job properly.