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the news must not be bruited abroad.'

'Yet Tiracorda confided this to his friend,' I observed.

'He evidently thinks that Dulcibeni knows how to keep his lips sealed. And Dulcibeni, like ourselves, is shut up in an inn under quarantine: he certainly has no opportunities to let out the secret. The most interesting thing, however, is not this.'

'What is it, then?'

'Dulcibeni was travelling with Fouquet, now he is visiting the Pope's physician to talk of mysterious things: farms, brothers, 'enter dumb into here'… I would give an eye to understand what they were talking about.'

While returning to the Donzello, we encountered the corpisantari, in their archives among the ruins under the Piazza Navona.

I noticed that the pair had reconstituted their filthy heap of bones, which now appeared to be considerably higher and more bulky. The corpisantari did not in any way salute our arrival: they were engaged in an intense discussion and appeared to be arguing over the ownership of an object. Ciacconio had the better of it, with a sudden ugly gesture grabbing something from Ugonio's hand and placing it, with an all-too servile smile, in the hands of Atto Melani. It was a few fragments of dry leaves.

'And what is this?' said Atto. 'I cannot possibly pay for all the stupid things that you would like to sell me.'

'It is an estranged foliage,' said Ugonio. 'To be more medicinal than mendacious, Ciacconio disgoverned it in the vicinity of the mortified, bloodified rodents.'

'A strange plant near to dead rats… how curious,' remarked Atto.

'Ciacconio says that it reeks in a stupefactual manner,' continued Ugonio. 'It is an excitifying, inquisitating, besotting plantation. In sum, to obtain more benefice than malefice, he is representing it to you, for by fulfilling one's obligations the Christian's jubilations are increased.'

Atto took one of the leaves; while he was raising it to the light of the lamp in order to examine it, I had a sudden reminiscence.

'Now that I come to think of it, Signor Atto, I too seem to have seen dry leaves in the galleries.'

'That is a fine one,' he commented, clearly amused. 'We are full of leaves down here. How is that possible? Trees do not grow under the ground.'

I explained to him that, when we were following Stilone Priaso in the conduit, I had trodden on dry leaves, so much so that I feared I might be heard by Stilone.

'Silly lad, you should have told me. In situations like ours, nothing should be neglected.'

Taking some of those friable vegetable fragments, I promised myself that I would make up for that inattention. Seeing that I was unable to help Atto to decipher the business of the farms, brothers and 'enter dumb into here' discussed by Tiracorda and Dulcibeni in the course of their incomprehensible conversation, I would at least endeavour to discover from what plant those dry leaves came: thus we might discover who had disseminated them throughout the underground galleries.

We left the corpisantari busy with their bones. During our return to the inn, I remembered that I had not yet reported to Abbot Melani my conversation with Devize. In the whirl of our recent discoveries, I had forgotten it, all the more so in that I had learned nothing of importance from the musician. So I told Atto of this encounter (obviously omitting the fact that, in order to gain the guitarist's confidence, I had cast a slur on the abbot's honour).

'Nothing of importance, did you say?' he exclaimed, without allowing me to finish. 'You are telling me that Queen Maria Teresa had contacts with the famous Francesco Corbetta, and with Devize, and you call that nothing of importance?'

Atto Melani's reaction took me by surprise: the abbot seemed almost beside himself. While I was recounting these matters to him, we would proceed for a short distance, then suddenly he would stop, open his eyes wide and ask me to repeat what I had said; whereupon he would again move on in silence, and then halt yet again, lost in thought. In the end, he had me recapitulate the whole story from the beginning.

So I told him yet again how, on my way to Devize's apartment to give him a massage, I had heard that rondeau which he so often played and which had so delighted all the other guests at the Donzello before the quarantine. I then asked him if he was the author of that piece and he replied that it was his master, one Corbetta, who had learned the melody of that rondeau during one of his frequent voyages. Corbetta had rearranged it and had made of it a tribute to the Queen; she had then handed the musical score to Devize, who in his turn had reworked it in part. In other words, it was not clear whose the music was, but we did at least know through whose hands it had passed.

'But do you know who Corbetta was?' asked the abbot, with eyes that had narrowed down to two slits, and stressing every single syllable.

The Italian Francesco Corbetta, he explained to me, had been the greatest of all guitarists. It was Mazarin who had called him to France to teach music to the young Louis XIV who adored the sound of the guitar. His fame had soon spread and King Charles II of England, another lover of the guitar, had taken him with him to London, had arranged a good marriage for him and had even elevated him to the peerage. However, in addition to being a wonderfully refined musician, Corbetta was also something else which almost no one knew: a most skilful master of ciphers and codes.

'Did he write letters in code?'

'Even better: he composed music containing ciphers, in which secret messages were encoded.'

Corbetta was an exceptional individual: both fascinating and intriguing, and a hardened gambler. For much of his life, he had travelled between Mantua, Venice, Bologna, Brussels, Spain and Holland, even becoming implicated in a number of scandals. He had died scarcely two years ago, in his sixtieth year.

'Perhaps he too did not disdain the profession of… counsellor, alongside the art of music…'

'I would venture to say that he was very much involved in the political affairs of the states which I have mentioned,' said Atto Melani, thus admitting that Corbetta must have had a hand in some affairs of espionage.

'And did he use the tablature of the guitar for that purpose?'

'Yes, but that was certainly not his invention. In England, the celebrated John Dowland, who played the lute at the court of Queen Elizabeth, wrote his music in such a manner that, through it, his patrons could transmit secret information.'

Atto Melani took no little time to convince me that musical notation could include meanings completely foreign to the art of sound. Yet, this had always been so: both monarchs and the Church had for centuries had recourse to musical cryptography. The matter was, moreover, familiar to ail men of doctrine. To give an example accessible to everyone, he said that in De furtivis litterarum notis Delia Porta had listed all the systems whereby secret messages of every kind and length may be encrypted. By means of a suitable key, for example, every letter of the alphabet could be associated with a musical note. The succession of notes, annotated on the pentagram would thus provide whoever held the key to the code with complete words and phrases.

'Thus, however, there arises the question of the saltus indecentes, or in other words, of disagreeable dissonances and disharmonies, which might even arouse suspicion in one simply casting an eye over the music. Someone then thought up more refined systems.'

'Who was that?'

'Our Kircher, to be precise: for example, in his Musurgia Universalis: instead of assigning a letter to each note, he distributed the alphabet among the four voices of a madrigal or an orchestra, the better to govern the musical material, thus rendering the composition less rough and disagreeable: after all, if the message was intercepted, such flaws would be enough to arouse suspicion in anyone. There are infinite possibilities for manipulating the sung text and the notes to be intoned. For example, if the musical note-'fa', 'la' or even 're'- coincides with the text, then only those syllables are to be taken into account. Or one can do the opposite, conserving only the remainder of the sung text which, at that point, will reveal its hidden meaning. It is, in any case, certain that Corbetta will have been aware of Kircher's innovation.'

'Do you think that, apart from his art, Devize will have learned from Corbetta this… art of communicating secretly?'

'That is just what is rumoured at the French court; especially as Devize was not only Corbetta's favourite pupil but above all a good friend of his.'

Dowland, Melani, Corbetta and now perhaps also his pupil Devize: I was beginning to suspect that music was