A working manuscript of Ludwig van Beethoven's Grosse Fuge sold to an anonymous buyer for $1.72 million, Sotheby's auctioneers said.

Sotheby's described the manuscript, found in a seminary library near Philadelphia, as "an astounding and important discovery" and possibly the most substantial manuscript of a Beethoven work to come up for sale in more than a century.

The buyer, who bid by telephone, paid $1.95 million, including the buyer's premium, Sotheby's said. It declined to say where the buyer was based.

"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," said Stephen Roe, head of Sotheby's manuscript department. "Its rediscovery will allow a complete reassessment of this extraordinary music."

The 80-page piano manuscript -- rediscovered this year by librarian Heather Carbo at the Palmer Theological Seminary in Wynnewood, Pa. -- is full of clues to Beethoven's composition process. It is written in brown and black ink, sometimes over pencil, and includes later annotations in pencil and red crayon. There is evidence of deletions, corrections, deep erasures, smudged alterations and several pages pasted over the original.

The manuscript is a piano duet version (Op. 134) of the last movement of Beethoven's String Quartet in B-flat, Op. 130, which was first performed in 1826, a year before his death.

University of Pennsylvania musicologist Jeffrey Kallberg, who authenticated the manuscript, said it was in pristine condition because it had not been touched or moved for so many decades.

"It's a very important discovery," he said. "This was a controversial and not understood work because it was so ahead of its time. It sounds like it was written by a dissonant 20th-century composer."

The autographed manuscript of Beethoven's Grosse Fuge in B-flat, lost for more than a century.