The Italian lyrics are as follows:
La cruda mia nemica
Del mio dolor si pasce
E si nutrica:
Perchè tal’hor sì pia
La veggio al mio languire
Che parmi udirla dire:
Spera ch’in breve finirà il tormento.
E poscia in un momento
Veggendomi contento
Mi si mostra sì ria
Ch’ancide il fior de la speranza mia;
Ond’è forza ch’io dica:
La cruda mia nemica
Del mio dolor si pasce
E si nutrica.
And my attempt to translate them into English looks like this so far:
My cruel enemy
Grazes on my pain
And feeds herself:
Because such ???? [piare = chirp?]
I see her to my to languish (???)
Which ??? me to hear her say (???)
Hope that soon the torment will finish.
And then in a moment
Seeing me content
She shows me how she laughs (?)
Which kills the flower of my hope;
So that it is [by?] force that I say:
My cruel enemy
Grazes on my pain
And feeds herself.
I copied the Italian lyrics from a printed score, which can be seen on p. 63 of this iPaper. It's possible I've made errors with things like accents and spellings in the transcription, but I double-checked everything pretty hard. In particular, the 'sì' in the phrases 'sì pia' and 'sì ria' very definitely does have a down-accent on the i, suggesting that it is not a pronoun or an 'if', but some form of 'yes'-type word. In fact, I Googled for similar phrases, and came up with a 16th-century poem by somebody called Tansillo that begins "D'invidia e D'amor Figlia sì Ria". But alas there was no translation of it, so I still don't know what to do with that construction.
As for the rest, I'm happy enough with the first three lines and most of the second half, but lines 4 to 6 ('Perchè...' to '...dire:') are the bit I've really got stuck with. Most of what I've put in my 'translation' there is little more than my attempts to parse each individual word - I can't get any overall sense out of these lines at all. The final translation doesn't need to be particularly polished or poetic or anything - I just want something fairly literal which will help me understand the madrigal.
Thanks in advance to anyone who can help!