We know it's terribly impractical, but we can only talk about sound in reference to the original language of the poem (i.e., Italian), since the aural tricks don't really work out in English. While some translations work hard to preserve the sound, a lot gets lost in translation.
And Petrarch really loves the sound of his poetry. You can tell this because he makes his words work hard to reach your ear by using just about every device in the book. In addition to the end rhymes in each stanza, Petrarch accentuates the meaning of his lines by using things like alliteration and internal rhyme. Take a look at stanza 1, when he asks God to intervene in Italy:
Vedi, Segnor cortese,
di che lievi cagion' che crudel guerra;
e i cor' ch endura et serra (10-12)
You see, gracious Lord,
what trivial reasons cause so cruel a war.
Those hearts enclosed and hardened (10-12)
The alliteration of the hard C (the C, if it's not before an I or E, and the Ch are pronounced so in Italian) emphasizes the harshness of the situation: the cruelty of war, the encrusted hearts. Sometimes, the use of verbal repetition exists just to sound cool. Okay, technically, it works to help the rhythm of the work, so that it pleases the ear when performed. Stanza 2 has a nifty bit of assonance going for it:
O diluvio raccolto
di che deserti strani
per inondar i nostri dolci campi.
Se da le proprie mani
questo n'avene, or chi fia che ne scampi. (28-32)
Although this deluge of I sounds isn't particularly meaningful, it sure will smack you in the ear when you hear it. The effect is most certainly there to help the cadence of the lines and perhaps even to help memorization of the work.
Stanza 4 has some truly gnarly examples of alliteration, but we'll start with a more run of the mill one in line 55: "Vostre voglie divise " ("Your disagreeing wills...").
But wait till you hit line 57: "Qual colpa, qual giudicio, o qual destino" ("What fault, what judgment, or what destiny"). In this case, the alliteration hooks up with anaphora to drive home the speaker's frustration at the ridiculous bloodshed.
Stanza 6 is, straight-up, an extravaganza of sound sensations, because it's really the emotional epicenter of Canzone 128. Petrarch opens it up with anaphora, which sets the tonal basis for the next few lines:
"Non è questo 'l terren ch' I' toccai pria?
non è questo il mio nido
ove nudrito fui sì dolcemente?
non è questa patria in ch' io mi fido,
madre benigna et pia" (81-85)
"Is this not the first soil my body touched?
Is this not my own nest
in which I found myself so sweetly nourished?
Is this not my own country I have trust in,
kind mother, merciful" (81-85)
Petrarch takes no prisoners when it comes to this kind of alliteration. He wants you to hear it, and he continues to get up in your ears throughout the rest of stanza 6 (check out line 89: "le lagrime del popol doloroso").
We could go on. But for the sake of your sanity, we'll just point out two convenient instances of internal rhyme. At the very end of stanza 3, Petrarch gives us this:
Mario aperse sì 'l fianco
che memoria de l'opra anco non langue,
quando assetato et stanco (45-47)
True, "fianco" and "stanco" are end rhymes. But sandwiched in between is "opra anco"—which would be pronounced like one word ("opranco")—and that is internal rhyme. Back to stanza 6, we get the partial internal rhymes focusing on "or":
combatter corto;
ché l'antico valore
ne l'italici cor non è ancor morto. (94-96)
We encourage you to check out Moro Silo's recitation of this poem in Italian. Believe us, it doesn't even matter if you don't understand Italian. It's worth it just to hear the collection of sounds that Petrarch uses to drive home his points in this poem.