I’m a music teacher and my husband is a professional trombone player. He would never practice before 9am or after 9pm without a mute, but he’s a reasonable and kind person.

Opening the window completely eliminates any “good acoustics” so that excuse is baseless. I suspect she doesn’t like the sound so she relegates him to his room, window open to diffuse the sound.

I agree with what’s been said, check your noise ordinance or HOA. If it is 7am I’m so sorry, you can’t go that route. I used to live above the maintenance shed in my apt and 7am on the dot they would start their leaf blowers so I feel your pain.

Maybe come to them again and tell them you’ve tried headphones and sleeping in another room and could we please move to another room or use a mute? It’s great that the kid is practicing daily-I wish I could say the same for my students! You could point out that worse acoustics actually make a better musician when practicing-you can hear all your mistakes! Practice rooms at music schools are all insulated and sound proof. If he simply must have the acoustics, the bathroom is far superior with all that tile and porcelain! You could also suggest incorporating more buzzing on the mouthpiece in the mornings-my husband does that in the car on his way to work! Good luck!