Tips for nipping hyper-focus in the bud?

Things have been great with my husband for the past few years.   However, he recently started playing music again and is quickly slipping into obsession.   Last night, he changed the strings on his guitar and then spent the next hour strumming it in the next room, when I finally brought up that he was annoying me, he insisted I couldn't hear it because it wasn't turned on, then he insisted that it wasn't as long as I was saying it was (of course, once it got annoying I started timing it because I knew this argument would come), then he went into the next room and continued to play it and acted like I was making up that I could still hear it.   (he moved about 10 feet away from where he had been before - no doors).  

Then we were going to bed, and he ran downstairs to finish a quick chore.  Half an hour later, I called him to see where he was and he was playing the guitar again.  I wouldn't have cared if he wanted to stay up and play, but I was staying up and had the overhead light on in the bedroom because he was right behind me.   When I pointed out that he was getting obsessive again, and told him that if he wanted to play guitar all night, all I wanted was for him to tell me so I wouldn't wait for him, he got really defensive.  

With a lot of ADHD issues, naming it often works for us.  It didn't work last night. 

We have been together for 25 years.  I know this spiral.   He's already forgetting things, coming home earlier than usual from work, and becoming more rigid and intolerant with the kids and me, as if we have all become more demanding of his time and attention, instead of acknowledging that he is just more interested in something else. It always ends with us fighting nonstop and him not changing until he HAS to, usually when he has lost his job.  

Is there any way to stop this obsessiveness?   I want him to be happy.  I want him to play music. I just don't want it to be more important than his job and family, and I don't want to give up things in my life just because he can't balance his.