LONDON (Reuters) - Beethoven is back with 51 seconds of a previously unknown composition that got its first public airing in a London auction house Thursday.

For more than 100 years, the single page of music, written by the German composer in 1817, lay hidden in a private collection of papers in a house in Cornwall, southern England.

It was discovered by Stephen Roe of Sotheby's auction house last August.

``I have reason to believe that this short piece is probably receiving its first performance ever, but we can't be sure of that. It's certainly the first performance in public,'' said Roe, who is head of Sotheby's books and manuscript department.

The manuscript is due to be auctioned by Sotheby's in December and is expected to fetch between 150,000 and 200,000 pounds ($250-$330,000).

``Nowhere is it mentioned in the extensive literature on the composer. The appearance of a new work by Beethoven at auction is almost certainly without precedent in modern times,'' Roe added.

Secrecy was at a premium before the brief but historic performance at Sotheby's. Even the musicians were only allowed to see the piece 20 minutes beforehand.

Musicians Praise Work

``It's a real treat, especially when you devote yourself to studying Beethoven works. It's a real gem, a real find,'' said Lucy Howard, a violinist in the Eroica string quartet.

``It is a short piece, but it's 23 beautiful bars of Beethoven, written at the height of his power,'' Roe said.

Ludwig van Beethoven wrote the short piece for a celebrated English traveler and critic, Richard Ford, who visited the composer in Vienna in 1817.

The manuscript is inscribed: ``This quartette was composed for me in my presence by Ludwig v. Beethoven at Vienna Friday 28th November 1817 Richard Ford.''

Nobody seems quite sure whether the piece was meant to become part of a longer work or whether it was meant as a one-of-a-kind souvenir.

The piece is in B minor, unusually for Beethoven, and Sotheby's said it was composed at a turning point in his career.

Between 1813 and 1817, Beethoven seems to have suffered a creative drought.

The manuscript was found in the home of the Molesworth St Aubyn family at Pencarrow in Cornwall, hidden in an album also containing a collection of letters and manuscripts by Verdi, Abraham Lincoln and Charlotte Bronte among others.