Both Uses of

theme

in

1984, by Orwell

Always they were a rehashing of the ancient themes—slum tenements, starving children, street battles, capitalists in top hats—
p. 76.8 *

themes = recurring ideas

The new tune which was to be the theme-song of Hate Week (the Hate Song, it was called) had already been composed and was being endlessly plugged on the telescreens.
p. 148.5 *

theme = most repeated

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)