I had to ask 3 times before the couple upstairs did something about their music.
They weren't playing it especially loudly and it was only in the day, but at they had their speakers on their wooden floor it amplified.
It took me ages to complain the first time, as I didn't want to be arsey. And I was really polite about it. I made it clear I wasn't actually asking them to turn it down, just to move their speakers off the floor. She agreed and then didn't do it. Eventually I got him and he did it straight away. Shame there isn't a more reasonable partner to deal with for you LRD.
She didn't have bad taste in music, but she did occasionally play modern, inferior (IMO) remixes of classic tunes. I would amuse myself then by putting the original on, much louder than her
(This was after I'd asked her to move the speakers.) This was one in particular I remember - reggae classic (actually that one's a remix too, but I'm getting pedantic now!)
It started again when she had a baby. Couldn't hear the baby crying(or if I did it didn't bother me, I can't remember now). But she used to play the same, inane, twee, absolutely rubbish kids CD on loop to her baby. It was awful! I swore when I had a baby I'd play them music that was actually decent, and thankfully I've stuck to that!
But I digress! I think it it's annoying you, you should ask again, if you think you can do it without antagonising him (might be tough if he's easily antagonised?)
I'd wait until he was doing it at an unsociable hour again so you have the moral high ground, and then be super apologetic, you're so sorry to have to come and bother him again, it's a such a shame the walls are so bad, but the noise means you can't sleep. Be nice. Unless he's a total arsehole, how can he have a problem with that?