This に means "and" basically.
We can say "はにかんだ声 and 透けた空" basically.
We have と which means "and," but this に is different from と.
In this example, はにかんだ声 comes first, then additionally 透けた空 comes next.
In other words, に shows a kind of direction. はにかんだ声 existed, then 透けた空 existed, too.
はにかんだ声と透けた空 can be the same as 透けた空とはにかんだ声.
But, 透けた空にはにかんだ声 is different from はにかんだ声に透けた空 because はにかんだ声 is more important compared to 透けた空.
This kind of usage of に is not common, I think. I'm using the Japanese dictionary called 広辞苑. It enumerates many meanings of に, this usage is the 17th explanation.
We need to take into consider that this phrase is a part of the lyrics. に is much better than と to rhyme with the previous line.