Our electrical grid is an amazing thing where your power can be coming from a solar panel this morning, a wind farm this afternoon, a fossil fuel plant this evening, and a hydro station overnight - with none of them being anywhere near you. On its way from the source to your speakers, that power goes a long way, through all manner of equipment, and past all sorts of sources of interference.
Every time the utility changes the source of your power, there will be a corresponding change in the "hash" that is induced on the power lines and comes along with it to your doorstep. It might be radio frequency noise coupled from a nearby radio station (near to a power line 100 miles from you) or an ultra low frequency created by the fluctuations of a 345KV line losing a varying amount of energy as it slowly swings in the breeze on a foggy evening and some power bleeds off as static energy.
As an electrical engineer who has done load flow analysis for utility companies, I have worked on power systems where they had thunderstorms in the power plant switchyard when the salt fog rolled in off the ocean, and the same system needed to put out 370KV at the plant to get 345KV out at the far end of the line. Most of the rest bled off into the air although some was lost to resistance heating and other equipment losses. What shows up at your door constantly goes through all kinds of waveform shaping, matching and combining of multiple power generation sources, weather conditions, temperatures, and equipment load variations - some planned, and some not.
Where I live, there are two predictable utility changes that happen every day. One is when the water company switches from one pumping station to another about 1:30 in the morning. For about 2 months some years back, there was enough difference in the water pressure to create a water hammer pulse in my area that was strong enough to trip the pressure alarm in my building's fire suppression system and we had 30+ families rousted out of bed until the fire department confirmed the true source of the call-in. There were a lot of really ticked-off people until the alarm company was able to tweak their settings to match the changes being made at the same time by the water plant.
On the electrical side, a similar thing occurs every evening as the power company changes the regional source of power to our community. Massive load changes that are seldom considered can include when a hydro system switches from providing power with their turbines all day and evening when loads are high and then switches to using those same turbine-generator systems to pump millions of gallons of water back up hill to a pumped storage reservoir overnight. That big supply becomes a big load, and the whole system must adjust accordingly. Again, it may be in another state, but it is part of your power supply.
Literally everyone's situation will be different, within your house, building, neighborhood, community, state and so on. Some people will have "cleaner" power at night, and others may find it is worse. With luck, each of us will find our "sweet spot" where and when what we hear is the best music to our ears.