Bruce Kovner, one of the world’s highest-earning investment managers, gave more than 140 manuscripts — together worth tens of millions of pounds — to the school.

They include the score for Beethoven’s piano version of his Grosse Fuge, bought for £1.12 million in London in December; the working manuscript of Beethoven’s Ninth Symphony, found in a vault after 150 years and bought for a record £2.1 million in 2003; the original manuscript of Rachmaninov’s Second Symphony, discovered in a cellar after almost a century; and the earliest manuscript of Purcell’s Dido and Aeneas.

The donation came with a further promise: Mr Kovner, who is chairman of the Juilliard where he once studied the harpsichord, has vowed to continue buying works and manuscripts for the college.

“I started collecting just for the personal pleasure of being close to these icons . . . At a certain point I realised that it would be better to make this collection available to the rest of the world rather than to keep it under a mattress,” said Mr Kovner.

A specially designed reading room is to be built to house the collection.

Mr Kovner, 60, the grandson of Russian immigrants, has built up a near-legendary reputation as a currency and commodities speculator. He is also vice-chairman of the Lincoln Centre and chairman of the American Enterprise Institute, the right-wing think-tank that inspired much of the neoconservative foreign policy of the Bush Administration.

His gift was greeted with astonishment in the music world. Professor Curtis Price, principal of the Royal Academy of Music in London, said: “This has turned the Juilliard into the premiere manuscripts collection almost overnight. Mr Kovner has been incredibly selective over the last ten years.

“He’s not just bought anything, but the rarest and best and most expensive manuscripts that have come on to the market. He’s obviously been very discriminating. It’s an absolute treasure trove of material.”

When the Grosse Fuge manuscript was sold, Mr Kovner was one of two rival bidders who concealed their identities by bidding over the telephone for the score, which had been discovered by chance last year at an evangelical seminary near Philadelphia.

The manuscript, which had never been seen by Beethoven scholars, contains more than 80 heavily worked and reworked pages. Composed in 1826 during the final months of his life when he was profoundly deaf, it is full of feverish amendments and passionate deletions in ink, pencil and red crayon, some so deep that they punctured the paper.

Christoph Wolff, a leading scholar and Professor of Musicology at Harvard University, said: “It’s quite remarkable. It really is a significant collection that covers 300 years of European and American music.

“It begins in the late 17th century and reaches the 20th. It has all the major players — Bach, Beethoven, Mozart, Schubert, Verdi, Stravinsky. They have been carefully chosen. This is not a collection of trophy manuscripts, but treasures.”

Mr Kovner, who is No 106 in Forbes magazine’s list of the richest Americans, founded Caxton Corporation, a trading company, and managed hedge funds. As a collector of rare books, he named the firm after the first English printer.

The Juilliard School — which was founded in 1905, as the Institute of Musical Art and whose graduates include Yo-Yo Ma, one of the era’s greatest cellists — took its name from Augustus Juilliard, a wealthy textile merchant, who died in 1919.

Explore Music

• CD Reviews

• Live Reviews

Editor's choice

• Burning Bush with W
• Greatest movie partnerships
• Nicole Kidman returns to Australia