It was hard to find just the right word for "la desdichada" -- it's literally "the unfortunate one," but if I just put that, then there is no indication that it's speaking of the woman he loved and not about the man who was crying and dying. We know it's the woman because "desdichada" is feminine -- no way to indicate feminine easily in English here. I went with "his ill-fated beloved" so that it's clear that "desdichada" refers to the one he's crying for.

Also in the chorus, "he was singing," and "he was laughing" would perhaps been better rendered "he used to sing," or "he would sing" -- but then the parellelism with "he was dying" would have been lost. I decided the parellelism was more important.

For clarity, I put [They say] before the phrases that begin with "que" (that)

"El mismo cielo" -- el mismo in this case is like how we would say "very" -- I almost rendered this "very heaven", but thought people might not recognize what I was doing, so I put "heaven itself."

"Las piedras jamás" is obviously the subject of "what would they know of loves" -- but it's a bit odd in the original, it just kind of hangs out there. So the English reflects that.

I had to put "every night" to indicate the multiple "noches" and I had to put "never slept" to indicate the continuing nature of "dormía" -- the never and every are carried by the verb construction of the Spanish, whereas that meaning is best conveyed in English by the addition of those words.