Now it follows that the better you are at expression, the better you have to be at understanding the language. If you're where Cuddly Human is and your expression is for most practical purposes limited to dynamics, then all you need to know is the meaning of each phrase. But if you are one of these intelligent and ultra-subtle baroque singers who can effectively use tone colour to pick out the emotions in individual words, it becomes a rather different matter. Further complications arise due to the way language changes over time, and if you are a baroque or early music singer you are certain to run into them. A word used by Monteverdi in one of his madrigals may or may not mean the same as it does in modern Italian, or it may not exist in modern Italian at all.
I'm not a language expert. I speak Penguin and understand English. Cuddly Human, however, does know something about languages, and especially about mediaeval and Renaissance Italian, and so without further ado I'm going to let her discuss translation with you. She does go on a bit, though, so I'll jump up and down if I think she needs to be brought to a conclusion.
Thank you, Charles - nice little blog you have here! What you didn't mention was that I am primarily a poetry translator, and song lyrics often have to be approached in a similar way, since they are usually poetic or semi-poetic in nature.
When I'm translating a poem, usually by Dante or Petrarch, I take great care to preserve or at least echo the rhyme and metre. (Sometimes it is not possible to keep exactly the same metre, as there are metres which work well in one language but not the other. However, I will always preserve as many features of the original as I can.) When I am translating song lyrics I don't normally do this, because the point of the translation is not to produce a polished piece for someone to read or even to sing. The only person who will see the translation is the singer I'm producing it for, and they will be using it strictly as a tool to help them work on the song in the original language. Nonetheless, most of the other considerations I use when translating poetry also apply to songs.
The thing about translation - and this is what makes a task like converting an Italian sonnet into an English sonnet possible at all, though it is still of the order of difficulty of a good cryptic crossword puzzle - is that there is never just one possible way to do it correctly. For any piece above a few words long, there are invariably very many possible accurate translations. The task of the translator is not to choose the most accurate - there are too many candidates for that position - but the most appropriate to the circumstances. Indeed it is very much like the task of the singer in interpreting a song, and ideally the singer and the translator should work closely together so that the two tasks mesh.
Let me take a concrete example in the shape of the first sonnet in Dante's Vita Nova. For the benefit of those who have no Italian I will not quote it in the original, but here is as plain and unadorned a prose translation of the last six lines as I can manage: "Love [a personification] seemed cheerful to me, holding my heart in his hand, and in his arms he held my lady asleep, wrapped in a cloth. Then he woke her, and of that burning heart she humbly fed, though she was afraid; then I saw him leave, weeping."
Now that is pretty weird stuff to the modern reader, not to say quite revolting. But what we have to remember is that Dante's original audience would have read it very differently, being much more used to metaphors of this type, not to mention having a completely different culture with a set of basic background assumptions and shared referents which were in some cases quite wildly alien from ours. This poem is a wonderfully stark example of the translator's dilemma which appears in a great deal of mediaeval writing. Do you translate the poem in such a way that it comes across to a modern audience as similarly as possible to the way the original poem came across to the original audience, or do you translate it so that it comes across to a modern English speaker with the same breathtaking oddness that would be experienced by a modern Italian speaker reading the original? There is no right or wrong answer to this, and I've translated poems at both extremes of this scale and various points along it, depending on my mood and the circumstances. Nonetheless, resolving the dilemma is particularly important when you have the needs of a singer to consider. If your singer wants to put his or her audience in the shoes of the composer's original audience as far as possible, you will need to select a translation that will jar as little as possible; whereas if the singer wants to show that this is something explicitly historical, and sees the audience as looking on from the present day, then if you find something odd or jarring in the text, you should avoid trying to soften it for modern sensibilities. Often the singer will not consciously be aware which approach they want to use, and it will come out only through discussion.
I could indeed, as Charles says, go on at some length, but since he's now jumping up and down as he warned me he might, I had better draw to a close here and say that if anyone wants to discuss any further the matter of translating for singers, they are more than welcome to do so in the comments.