How does the Rabbi explain the Jewish law principle that “a woman’s voice is nakedness”?

“A woman’s voice is nakedness” was not originally said specifically about singing. The halakhic decisors narrowed it to singing.
But in any case, the prohibition applies only where it leads to forbidden erotic thoughts. But if a person goes there for the sake of the art, or even just for entertainment, and the performance is modest and not sexually arousing, I do not see any prohibition in it.