Both Uses

theme
in
Take the Tortillas out of Your Poetry
(Edited)

If we leave out our tortillas—and by that I mean the language, history, cultural values, and themes of our literature—the very culture we're portraying will die.
*

themes = recurring ideas
Let me return to the theme of reading and books.

theme = basic idea

Definitions:

(1) (theme as in: theme of the novel)
a basic idea that underlies what is being said or done -- especially in a literary or artistic work
(2) (theme as in: musical theme)
the initial or primary melody of a musical composition

or

(as in "theme song") music that is most repeated in a film, television series, or other theatrical production
(3) (theme as in: wrote a 2-page theme on my summer)
an essay written by a student

(This sense of theme is much rarer in recent decades than in the past.)
(4) (meaning too rare to warrant focus)