Are music reality show questions on-topic?
Good question. Their status on Movies & TV seems a bit vague, and it's unclear if they're a good fit there.
Personally, I think that questions regarding music or musicians should be on topic here even if the music or musician in question perform as part of a reality TV show, but questions about the show (its production, hosts and so on) shouldn't be.
I would say yes. If the question is a Q&A format, why not?
I, personally don't watch these kind of shows, but there are Music Fans that do.
I think - as always - "it depends"
Who do you think will win this year's X Factor?
is as far off-topic as it can get.
Don't you think so&so was out of tune on Sunday?
However, Leona Lewis/JLS et al have far outgrown their reality show beginnings & would be a valid topic of conversation (whether I like them or not;)
There is no reason to declare this questions as off-topic.
The music reality show part could be an important part of the carrer of a musician, and there is no reason to forbid people asking about it. But as any other question, it has to respect standard SE rules.
I think NO. Music reality shows are TV shows, and so are not appropriate or relevant to a Q&A site about music.