first off, I just want to double check, you talking MusicBrainz style? I believe MusicBrainz and BookBrainz title styles are very similar, if not identical, I’m mostly asking so this thread can be correctly categorized~
that said, capitalizing the ‘S’ just feels wrong to me too. since there’s an apostrophe, that could mean the word the ‘S’ belongs to has been ‘cut off’ (I forget the correct term), meaning it represents ‘is’ or ‘has’ or some other option I can’t think of at the moment.
that would be my rationalization if I were to add this track/release/whatever.
I will also double check, you’re sure the title isn’t supposed to be [Artist]’s Wonderful?
It’s the first letter of a title, so it should be capitalized. It actually should always be capitalized. Most capitalization guidelines I’ve found online say when apostrophes are present you always capitalize the first letter of any word that would be ordinarily capitalized. So, 'til, should always be 'Til; 's, always 'S, 'cause, always 'Cause, etc. But first & last letters of titles are always capitalized regardless of apostrophes. even 'n, etc. which ordinarily wouldn’t be capitalized. It looks odd sometimes, but it’s the correct way.