Is Postcolonial Literature Only Books?

What all does the term “postcolonial literature” encompass? Is it just prose and poems? Or can it include albums, musicals, and other theatrical works? And what exactly¬†was¬†the British Empire, and what countries were part of it? In our research, we looked at the historical construction of the Empire, and the theatre and music works that came from postcolonial British authors.