The 'Liber scriptum' was originally set as a choral fugue. However, in the spring of 1875 Verdi decided to turn that into a solo for his mezzo-soprano, Maria Waldmann. He did not include it in the Paris performances of that year, chiefly because, as he told the singer: "The public's first impressions are always terrible, and even should this piece make its effect, people would say, 'It was better as it was before'".
The mezzo-soprano solo had to wait until mid-may 1875, and the London-audience was the first to hear it.
It is a superb example of declamatory melody articulated in three massive periods each following the tercet design of the poem.

1.'Liber scriptus proferetur' - is a typical instance of late Verdian three-limbed melody. The first two phrases are identical, both featuring the rising fifth like a finger raised in warning, followed by a menacing death-figure on the timpani. The third phrase is equal in length to the other two combined yet it evolves so freely that all sense of regularity is obliterated.

2. 'Judex ergo cum sedebit' - is an expanded counterpart of the first period. It is introduced by a blazing brass chord in the major - the search-light gaze of the Supreme judge from whom nothing is hid..

'Judex ergo cum sedebit' - realaudio

its first two phrases are similar but not identical, being of four and five bars respectively. The third phrase proceeds for seven bars before merging into the corresponding phrase of the first period.

3. the third period is a kind of coda, where both the preceding strophes are sung once more: The first over a pounding harmonic pedal that breaks off on a fortissimo diminished seventh, The second muttered over shifting harmonies that seem to give way beneath our feet, the soloist trailing into incoherence and repeating 'Nil' as the bass had repeated 'Mors' with a growing sense of emptiness. But here the device has another purpose: that of lulling the listener into a state of unpreparedness for the thunderbolt of the final phrase.

Mors stupebit - that was the bass in the tuba mirum -

Nil inultum - This is the mezzo-soprano now. notice the similarity.

Throughout this movement the chorus had contributed no more than an occasional murmured 'Dies irae'. Now they combine with the orchestra in a furious crescendo leading to a restatement of the 'Dies-irae-theme'. This intensifies the religious and musical content of the 'Liber scriptus'.
The Chorus dissolves slowly to make place for the following section.