Oh then as others say, I honestly would not even consider music.
DD (sorry to keep quoting my DC but it's not a terrible ref point) was about grade 4 IIRC (she did grade 6 in year 12 I think so 4 in year 9 sounds rightish) and had also done theory as part of her music lessons.
Now the exam spec has changed as she has a letter grade but I think there is now more focus on composition. DD found that aspect tough though she excelled at the theory (ie the written exam). Performance was fine. She got a B and as a result canned a plan to take A level.
What does the school music teacher say? Honestly taking GCSE music without playing an instrument with lessons is a bit like taking GCSE PE without playing a sport beyond kicking a football with your mates.
Unless yes is it music Btec? That is less based on formal music theory and composition I think?
I suggest art if it's a passion, as @MeetMeOnTheCorner says, the GCSE is a good foundation for art A level and other art-related subjects post 16.
Are they aware of the portfolio needs of photography? I was going to say drop that but now I think drop the music.
What is the motivation for these choices @GCSEQuestion2288? Is the YP very arts-engaged? Or do they just not like the other options? As a PP suggested, business might be an interesting option and perhaps not too essay/fact heavy if that is indeed the issue.