It is good to have a broad spread of subjects at GCSE. This however, can mean a number of different things. Having to study Eng, Maths and sciences ensures some breadth straight away. Often people are encouraged but not forced to do a language and a humanity.
What would a narrow curriculum look like? Perhaps one where all of the options were practical arts - so music, art, drama, photography. So here there is no humanity or language.
Alternatively, narrow might be all computer based and DT options.
Perhaps is either language or humanity is missing, it's fine, but if both are missing it's worth considering why.
And then there's the thing about showing you are academic at GCSE. Having a good range of academic subjects at GCSE and Hugh grades does show this. Academic children are usually capable of doing a language and a humanity and doing well. If however, they have a good range of academic subjects at high grades, missing a language or a humanity won't make it look non-academic.
What might make it look non-academic - well firstly low grades, so it's important to do things you can do well in. Perhaps if all of the options chosen looked like practical subjects. Nothing wrong with having a practical subject, but perhaps 4 doesn't look academic.
For academic children, I'd generally say, allow yourself one totally free choice regardless of academics if you want to, it won't be a problem if the rest is academic.
And remember that music is highly regarded and could certainly be seen an academic.