In 1969 the Institute of Verdi Studies in Parma convened an international congress on the subject of Don Carlos. Fifty-two papers were read, and the proceedings fill a fat volume of over 600 pages. Two speakers had looked beyond the printed sources: Ursula Gunther had examined the autograph of Act I, in the Bibliothèque Nationale, and David Rosen had discovered, folded down in the conducting score used for the first performance, and still in the Paris Opera library, a hitherto unknown section of the Philip/Posa duet which Verdi had cut before the premiere. He also found evidence for other pre-performance cuts, in the form of stub-ends of pages which had been literally cut from both the autograph and the conducting score; some opening and closing bars remained. A few months later I found this ‘lost’ music, in the original orchestral parts, still preserved at the Opera: the cut passages had simply been stitched or pinned together, or pasted down; the same had happened in the singers' scores. Line by line, it was possible to reconstruct a good deal of totally unknown music by the mature Verdi.