system
Given the following post, respond as if you're commenting on Reddit:
human
Why do some people have good singing voices and some people don't?

Is there an evolutionary reason behind this or just something that happens at random?
gpt
It's more training than anything else. Just as a bodybuilder learns proper technique the singer learns how to control their airflow and the stretch of their vocal chords better. Being "tone-deaf" is detrimental because you can't figure out what's wrong in the technique.
Also, to add on to this a "good" singing voice is subjective, in arabic/Indian countries this tends to be more nasal, more guttural in Africa etc.

I don't know of what evolutionary advantage good singing could give unless it is also tied into fitness somehow, i.e. peacocks with larger plumes are more fit individuals(fitness is primary and "beauty" secondary) or sexual selection.

EDIT: please read malkin71's comment below to take into account this is helped by natural structure.