In Canto 2 of the Purgatorio, when Dante describes arriving on the shore of Purgatory, one of the first indications of the condition of the souls in Purgatory is their ability to hold music in their mind and to remember music. The first soul that Dante meets in Purgatory is Casella, a composer and musician: Dante wonders if Casella has had his memory of music taken away from him; Casella responds by singing; and the poet states that this continues to sound within him. It is as though the inner music indicates continuity across the living and the souls of Purgatory.
«Se nuova legge non ti toglie
memoria o uso a l’amoroso canto
che mi solea quetar tutte mie doglie,
di ciò ti piaccia consolare alquanto
l’anima mia, che, con la sua persona
venendo qui, è affannata tanto!».
‘Amor che ne la mente mi ragiona’
cominciò elli allor sì dolcemente,
che la dolcezza ancor dentro mi suona.
(Purgatorio 2, lines 106-114)
[“If there’s no new law that denies
you memory or practice of the songs
of love that used to quiet all my longings,
then may it please you with those songs to solace
my soul somewhat; for—having journeyed here
together with my body—it is weary.”
“Love that discourses to me in my mind”
he then began to sing—and sang so sweetly
that I still hear that sweetness sound in me.]
One of the features of Dante’s Purgatorio is that readers are frequently invited to imagine and remember heard song; this occurs earlier in Purgatorio 2, when a group of souls arrives at Purgatory singing a Psalm, and the text invites readers to imagine the whole of the song:
‘In exitu Isräel de Aegypto’
cantavan tutti insieme ad una voce
con quanto di quel salmo è poscia scripto.
(Purgatorio 2, lines 46-48)
[“In exitu Israel de Aegypto,”
with what is written after of that psalm,
all of those spirits sang as with one voice.]
This technique – using a short extract of liturgical song and requiring the reader to imagine the rest – marks a distinct new phase in how Dante engages his readers in the Commedia.
More details here.