The time comes to turn the attention on the individual sinner.
The 'quid sum miser' is a trio for soprano, mezzo-soprano, and tenor. Two clarintes and a bassoon open the musical discourse with a cadential figure like an idiogram of grief that recurs like a refrain. But as often with Verdi it does not reveal its full identity at the outset. Not till the third occurrence does it acquire that F sharp that gives it its unique poignancy.

'Quid sum miser - refrain motive' -realaudio

So too with the intervening vocal entries.
The mezzo soprano's first phrase, a setting of the first line of the tercet, is brought to a cadence after four bars. When she resumes it to the remaining two lines it flowers into something like a theme. Next the tenor takes it up the other two voices joining in, to produce a still longer variant. A third and final period begins an unaccompanied trio in the relative major but like the preceding two returns inexorably to the same cadential phrase of clarinets and bassoon. In this way a tentative opening has solidified into a species of bar-form with refrain. Another binding element is the purling bassoon pattern which forms the instrumental bass throughout.
The coda alternates major and minor with a sweetness worthy of Schubert; but the sense of consolation is precarious, and the soloists are left repeating one by one the three questions on rising levels of pitch.
This section ends suspended like a question, which is answered brutally in the next one.