epaired and rebuilt so many times they can hardly be called original。 Only six Strads； for example； retain their original necks。 When you drop a violin； it's always the neck that breaks。 But there are about ten or twenty that sound almost perfect。〃
〃Why？〃
At this； the man smiled。 〃That； of course； is the question。〃 He rose； went to the steel door； unlocked it； and swung it open； revealing two hard…disk recording workstations and racks of digital samplers； pressors； and limiters。 The walls and ceiling were covered with acoustic foam paneling。
They followed him in； and he shut and locked the door behind them。 Then he switched on an amplifier； pulled up the faders on a nearby mixing console。 A low hum began to sound from the reference speakers set high in the walls。
〃The first really scientific test done on a Stradivarius was performed about fifty years ago。 They hooked a sound generator to the bridge of a violin and had it vibrate the instrument。 Then they measured how the violin vibrated in return。 An absurd test； really； because it has nothing to do with the way a violin is played。 But even such a crude test showed the Strad gave back an extraordinary response in the two…thousand…to…four…thousand…hertz range…which； not at all coincidentally； happens to be the range of sound that the human ear is most sensitive to。 Later； high…speed puters allowed real…time processing of a Strad being played。 Let me give you an example。〃
He turned to one of the digital samplers； used an attached keyboard to select an audio sample； sent the output to the mixer。 The sweet sound of a violin filled the room。
〃This is Jascha Heifetz playing the cadenza of Beethoven's violin concerto on the Messiah Stradivarius。〃
A plex series of dancing lines appeared on a monitor sitting behind the mixer。 Spezi pointed at them。
〃That is a frequency analysis from thirty to thirty thousand hertz。 Look at the richness of the low…frequency sounds！ They give the violin its darkness； its sonority。 And in the two thousand to four thousand range I mentioned； see how lively and robust it is。This is what fills the concert hall with sound。〃
D'Agosta wondered what any of this had to do with Bullard or the murders。 He also wondered what Pendergast had written on the business card the man was still clutching in one fist。 Whatever it was； it had clearly made this man remarkably cooperative。
〃And these are the high frequencies。 Look how they leap and flicker； like the flame of a candle。 It's these transients that give the Strad that breathing； trembling tone； so delicate and fleeting。〃
Pendergast inclined his head。 〃So； Dottore…what's the secret？〃
Spezi reached for the sampler and the music stopped。 〃There is no one secret。 It was a whole catalog of secrets； some of which we've cracked； others we haven't。 For example； we know exactly what kind of architecture Stradivari used。 With puterized tomography； we can map a Strad perfectly in three dimensions。 We know all there is to know about Stradivari's designs for the belly； backplate； purfling； f…holes…everything。 We also know just what types of wood he used。 We can make a perfect copy。〃
He turned to one of the puters； typed again； and the image of a beautiful violin appeared on its screen。 〃There it is。 An absolutely perfect copy of the Harrison Strad； down to the very nicks and scratches。 It took me almost half a year； back in the early eighties； to plete。〃 He glanced over at them with a mirthless smile。 〃It soundsdreadful 。 The real secret； you see； was in thechemistry 。 Specifically； the recipe for the solution Stradivari soaked his wood in； and the recipe for his varnish。 This has been the thrust of my research ever since。〃
〃And？〃
The man hesitated。 〃I don't know why I am inclined to trust you； but I do。 The wood Stradivari used was cut in the foothills of the Apennines and dumped green into the Po or Adige Rivers； floated downstream； and stored in brackish lagoons near Venice。 This was purely for convenience； but it did something critical to the wood…it opened up its pores。 Stradivari purchased the wood wet。 He did not season it。 Instead； he soaked it further in a solution of his own making…as far as I can deduce； a bination of borax； sea salt； fruit gum； quartz and other minerals； and ground； colored Venetian glass。 He soaked it for months； perhaps years； while it absorbed these chemicals。 What did they do to the wood？ Amazing； plex； miraculous things！ First； they preserved it。 The borax made the wood tighter； harder； stiffer。 The ground quartz and glass prevented the violin from being eaten by woodworms…but it also filled in the air spaces and gave it a brilliance and clarity of tone。 The fruit gum caused subtle changes and acted as a fungicide。 Of course； the real secret lies in the proportions…and those； Signor Pendergast； I will not tell you。〃
Pendergast nodded。
〃Over the years； I've made hundreds of violins from wood treated this way； experimenting with the ratios and the length of time in solution。 The resulting instruments had a big； brilliant sound。 But it was aharsh sound。 Something was needed todampen the vibrations； the overtones。〃
He paused。 〃Here is where the true genius of Stradivari es in。 He found that in his secret varnish。〃
He moused up the puter screen； clicked through a few menus。 A new image appeared in black and white； a landscape of incredible ruggedness； looking to D'Agosta like some vast mountain range。
〃Here is the varnish of a Stradivarius under a scanning electron microscope； 30；000x。 As you can see； it is not the smooth； hard layer it seems to the naked eye。 Instead； there are billions of microscopic cracks。 When the violin is played； these cracksabsorb anddampen the harsh vibrations and resonances； allowing only the purest； clearest tone to escape。 That's the true secret to Stradivari's violins。 The problem is； the varnish he used was an incredibly plex chemical solution； involving boiled insects and other organic and inorganic sources。 It has defied all analysis…and we have so little of it to test。 You can't strip the varnish off a Strad…removing even a little will ruin a violin。 You'd need to destroy an entire instrument to get enough varnish to analyze it properly。 Even then； you couldn't use one of his inferior violins。 Those were experimental； and the varnish recipe changed many times。 No…you'd have to destroy one from the golden period。 Not only that； but you'd need to cut into the wood and analyze the chemistry of the solution he soaked them in as well as the interface between the varnish and the wood。 For all these reasons； we have not been able to figure out exactly how he did it。〃
He leaned back。 〃Another problem。 Even if youhad all his secret recipes； you still might fail。 Stradivari； knowing all that we don't； managed to make some mediocre violins。 There were other factors to making a great violin； some apparently even beyondhis control…such as the particular qualities of the piece of wood he used。〃
Pendergast nodded。
〃And that； Mr。 Pendergast； is all I can tell you。〃 The man's face glittered with feverish intensity。 〃And now let us speak ofthis 。〃 He opened his hand and smoothed the crumpled business card。 And for the first time； D'Agosta glimpsed what Pendergast had written on it。
It was the word Stormcloud 。
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The man held out the card in a trembling hand。
Pendergast nodded in return。 〃Perhaps the best way to start would be for you to tell Sergeant D'Agosta what you know of its history。〃
Spezi turned to D'Agosta； his face filling with regret。 〃The Stormcloud was Stradivari's greatest violin。 It was played by a string of virtuosi in an almost unbroken line from Monteverdi to Paganini and beyond。 It was present at some of the greatest moments in the history of music。 It was played by Franz Clement at the premiere of Beethoven's violin concerto。 It was played by Brahms himself at the premiere of his Second Violin Concerto； and by Paganini for the first Italian performance of all twenty…four of his caprices。 And then； just before World War I…on the death of the virtuoso Luciano Toscanelli； may God curse him…it disappeared。 Toscanelli went insane at the end of his days and； some say； destroyed it。 Others say it was lost in the Great War。〃
〃It wasn't。〃
Spezi straightened abruptly。 〃You mean it stillexists ？〃
〃A few more questions if I may； Dottore。 What do you know of the ownership of the Stormcloud？〃
〃That was one of its mysteries。 It was always owned by the same family； apparently； who it was said purchased the instrument directly from Stradivari himself。 It was passed down from father to son only in name； being on continuous loan to a string of virtuosi。 That's normal； of course： most of the Strads today are owned by wealthy collectors who turn them over to virtuosi to play on long…term loan。 Just so with the Stormcloud。 When the virtuoso who was playing it died…or if he had the misfortune to give a bad concert…it was taken away by the family that owned it and given to another。 There would have been intense petition for it。 No doubt that is the reason the family remained anonymous…they didn't want to be harried and importuned by aspiring violinists。 They made s