As mentioned on STYLE-881, Portuguese guidelines do not specify what to do with track titles that include parentheses. This leads to questions on titles like Você me vira a cabeça (Me tira do sério) which could be capitalized as “Você me vira a cabeça (Me tira do sério)” or as “Você me vira a cabeça (me tira do sério)”.
I’m not a Portuguese speaker, so I won’t claim to know how this should be done, but I generally like the option used in the Estonian guidelines for these cases:
The first word of an alternative title in parentheses should be capitalized
If the parentheses do not contain an alternative title, but a continuation of the preceding phrase, it shouldn’t be capitalized
So that would be my preferred choice if that makes sense in Portuguese (it does in Spanish, which is close, but) But I’m hoping to see actual Portuguese speakers give their opinions here!