I’ve noticed the same thing, OP. Music sounds better at night. There are a few things that might cause this:
1) Less businesses operating which otherwise make for dirtier power lines.
2) Your perception physically changes. Afterall, it’s night time - you need to be able to hear the jaguar in the bush because you can’t see it. Your brain is most assuredly making different neurotransmitters at night.
3) A better ground. (I actually put a lot of faith in this one even though I don’t have measurements.) When the sun shines on Earth, it excites electrons in the ground (this is called circadian “charge” or something like that name.) The dark side of Earth doesn’t receive this charge. The charge flows from light side to dark side - these are called tellurian currents. They are measurable at dusk and dawn. Of all the places you can be (light side, dusk, dawn or dark side) the dark side will have the least electrical activity in the ground.
4) Some combination of the above.
5) None of the above.
Instead of fighting it, I’ve come to embrace it: “Oh, it’s night time, I bet my audio system sounds great! Let’s go listen.”
