Peking Opera belongs to the music category?

Strictly speaking, it does not belong to belong to the opera in China opera is and the ancient Greek theater to be compared to the opera is a comprehensive stage art, music is just an aspect of the opera only. Singing and accompaniment are considered music, but the core of Beijing opera is that it is storytelling and performance, not just singing and playing. That's why opera singers are usually members of the Dramatists Guild rather than the Musicians Guild.