But now: why does "bocca baciata non perde ventura - anzi rinnova, come fa la luna"?
Poetry slang, as I was saying. Let me walk you through it.
Dal labbro, il canto estasiato, vola: a sound stems, in what Boito stupendously calls aer antelucano - "the night air before the light", the Darkness of the Eden (finché non splende in ciel notturna face - as Susanna would have put it).
If no one replies, to that sound - if it stays an unmatched, single event - it is perceived as random, hence soon forgotten.
If instead someone does, reply, to that sound, but with a completely different one - the result is perceived as chaotic, not as a match - hence, again, is soon forgotten.
BUT. When a sound is matched by its equal, and, that is, by a rhyme, a prodigy happens: a spell.
A spell of Time is defined: Time itself is born with the repetition of Light.
A Moon cycle is a form of visual rhyme.
A rhyme is the repetition of something (of something identical when the rhyme is perfect, or, in Italian, kissed: rima baciata) bringing in itself an information about the length of a spell of time: that occurring in between the two matching events, the two kisses - or smacks of lips.
What is matched by a kissed rhyme allows the computation of Time, eases memory and won't be forgotten: bocca baciata non perde ventura.
Poetry is to remember, and be remembered.
Everything else will be lost.
All things stored in a stanza not locked by a chiave will be lost.