Passed down through generations of Horsleys, this compilation is now going under the hammer at Sotheby's, where musicologist Simon Maguire digs it out of its plastic wrapper - not so much Lot 1, more Exhibit A - to show me.
A black leather case the size of a large postage stamp, out of which he draws a tiny book: and as he thumbs through it, my brain begins to spin. There is a piano variation from Brahms, a chordal flourish by Liszt, a snatch of Mendelssohn's teenage Octet, and a complete song by Chopin, rendered in a minute version of that composer's always-fastidious hand. There are Hummel, Strauss, Meyerbeer, and Clara Schumann defiantly giving her maiden name. Here are all the virtuosi of the day interspersed with Dickens, the brothers Grimm, the computer pioneer Babbage, and drawings of astonishing fineness from Winterhalter, Landseer, and Isambard Kingdom Brunel.
Some of these would still be impressive if magnified a thousand times: one forgets how well the educated people in pre-camera times - Mendelssohn included - could draw. Macro in micro: it's a whole world Maguire holds in his hand.
The reserve is pounds 25,000, and he expects it to be bought by a collector rather than an institution: it's too small and fragile to be pored over by scholarly hordes. "And it's not the sort of thing a dealer would go for - it's not an album which lends itself to being broken up."
He sometimes finds himself being offered album-pages from books he had previously known in their undismembered state: the 19th-century mania for grabbing sacred relics of musical heroes - which began with the dismemberment of Beethoven's sketchbooks - lives on for speculators to profit from.
But curiosities like this, says Maguire, are not what the market is primarily about. "Its real heart is the messy sort of stuff Brahms always tried to destroy: manuscripts which show composers working out their ideas." In this same sale punters are offered a Mendelssohn song manuscript (reserve pounds 12,000) which reveals that normally polished master in an uncharacteristically unsure frame of mind. The piece de resistance (pounds 100,000) will be the only surviving manuscript in Schubert's own hand of his first mature piano sonata. Big pieces like this are now increasingly rare: Schubert manuscripts are only on the loose because 19th-century institutions didn't think them worth acquiring. But now they too have joined manuscripts of the other great composers on their one-way journey to captivity. The Schubert's likely buyers include the Austrian National Library and the Vienna Staatsbibliothek, both keen to reclaim their heritage, as German libraries are to claw back Beethoven and Brahms.
Should we be glad when a manuscript is bought by a public institution, rather than a private gloater? Not necessarily. There is an honourable tradition in America whereby owners of manuscripts loan them to the Morgan Library, so scholars can study them. On the other hand some of the biggest institutional collections in Europe are strikingly resistant to scholarly access. As a Bellini-expert, Maguire periodically needs to examine scores whose autograph manuscripts are in the Naples Conservatory, but he can't get in: Italian bureaucracy now bars all except Neapolitan music students. Even the British Library makes things difficult, trying to fob scholars off with microfilm.
It's not often realised what a massive chunk of the world's musical treasure sits in the British Library, whose bosses must be praying that Germany and Austria don't get infected by the musical equivalent of Greece's lust for the Marbles.
They hold most of the important manuscripts of Bach's 48, and some complete Haydn symphonies; they have the monopoly on Mozart string quartets. Moreover, they have an amazing Handel manuscript collection, the result of the composer's bequest to his amanuensis being passed on to George III, who put it into the Royal Music Library, which was in due course absorbed by the British Museum. That is why Handel manuscripts are now rare, and why not one note from his hand has passed through Sotheby's in the last five years.
The distinction between "autograph" manuscripts - in the composer's own hand - and con- temporary copies is crucial. In the 18th century, when printing was more expensive than copying by hand, the composer's original autograph manuscript was often discarded once the scribe had produced a fair one. Hence the conundrum posed by the Scarlatti "scribal manuscript" which, at pounds 2,000, is one of the cheaper items in Sotheby's sale.
Though scholars have spent decades combing Spain - where Scarlatti spent his last 30 years - not one autograph manuscript of his 550 sonatas survives; all we have is authenticated copies. Maguire, who has played through the 21 sonatas on offer, thinks them inferior to many of Scarlatti's known ones, but he still feels obliged to leave the question open.
"You could buy them and find you had some acceptable Scarlatti sonatas, but I don't know how you'd prove it. On the other hand, I don't know how you could logically prove or disprove the 550 that are accepted already. I'd say the new ones are worth a punt." A miasma of doubt can be powerfully good for business.
Sotheby's may have cornered the market in manuscript auctions, but there are other players in the game. The Covent Garden dealers Travis and Emery are doing excellent business with first editions of Britten and Vaughan Williams.
"People come in every week saying, `My grandmother's died and left a garage-full of music', and we go and look at it," says a spokesman. "There's no problem getting hold of stuff."
And according to Lisa Cox, who advertises her wares on the Internet, the market has never been more buoyant.
"Puccini letters tend to stick, but you'd make an absolute killing with the manuscript of Madam Butterfly, while first editions are going through the roof. Two guys in America have just come on the market who can outbid any institution, and they've had a galvanising effect."
Good clean fun? Well, the thrill of this chase is not merely financial, and, with composition increasingly taking place on computers, the source will eventually dry up. What am I bid for this printout? Going, going, gone.
Sotheby's forthcoming music manuscript sale is on 9 December