It's how it was recorded. Either the recording has or it doesn't. If it does, even a moderate quality system (with attention paid to setup) will reveal this effect.
Which component is most responsible?
I anticipate this question will garner varied opinions, which I look forward to reading: Which component(s) is most responsible for hearing clear, distinct separation of voices in a chorus or when listening to multiple background vocals, as I often hear audiophile speak of.
Thanks.
Thanks.