Commentary Purg XXXII 61-62

Dante leaves us with another of his little mysteries.  What was the 'hymn' that he heard sung but could not understand, except to know that it is not sung on earth?  Dante tells us as much and, as a result, the Ottimo (DDP Ottimo.Purg.XXXII.61-66) reasons, we cannot identify it.  However, is there a hymn, known to be sung in Heaven, that we on earth have never heard?

      The word inno (hymn) occurs six times in the poem in five passages ([Inf VII 125]; [Purg VIII 17]; [Purg XXV 127]; [Purg XXV 129]; here; [Par XIV 123]).  In the occurrences previous to this one the word has been used once antiphrastically, to denigrate Plutus's unintelligible shout, and then, in its next two appearances, to refer to the hymns 'Te lucis ante' and 'Summae Deus clementiae,' respectively.  In other words, until now inno has either been used antiphrastically and thus in a general sense (i.e., 'an utterance not like a hymn') or with exactitude to indicate a particular Christian hymn.  (For the final appearance of inno see C.Par.XIV.118-126.)  Are we supposed to be able to identify this song?  There are, one must admit, times at which Dante leaves melody a mystery; even twice in this very canto (the 'angelica nota' [angelic song] of [Purg XXXII 33] and the 'più dolce canzone' [song more sweet] of [Purg XXXII 90], his references have successfully resisted identification).  It would be unusual for Dante to have introduced a riddle without offering us the grounds for solving it.  We are looking for a song with two characteristics: it must be unknown on earth and it almost certainly must be in celebration of Jesus's victory over death.  Is there such a song?  John of Serravalle (DDP Serravalle.Purg.XXXII.46-48) thought so: the last book of the Bible speaks of a canticum novum (new song) that is sung before the throne of God (Rev. 14:3), a citation found, surprisingly enough, only once again in the commentary tradition (Steiner [DDP Steiner.Purg.XXXII.61-63] and then possibly again, referred to glancingly but not definitively by Trucchi [DDP Trucchi.Purg.XXXII.61-63]).  Kaske (Kask.1974.1), pp. 206-7, however, while unaware that he had at least two precursors, also sees a reference here to the canticum novum of Revelation.  Kaske cites Revelation 5:9, which is also apposite, if the similar passage at 14:3 has a certain priority, as we shall see.  In Revelation 5:6 Christ comes as a slain lamb to judge humankind, at which the twenty-four elders and the four Gospel beasts lower themselves before the king (5:8) and sing a 'new song' (canticum novum): 'You are worthy to take the book, and to open the seals thereof; for you were slain and have redeemed us to God....' (5:9, italics added).  A related passage (14:3) deepens the resonances with Purgatorio XXXII: 'And they sang as it were a new song [canticum novum] before the throne, and before the four beasts and the elders; and no man could learn that song but the hundred and forty and four thousand, who were redeemed from earth' (italics added).  It seems clear both what the song was and why it is not sung on earth.  For the number of those in the procession as 144, the number of the 144,000 thousand of the Church Triumphant, see C.Purg.XXIX.145-150.