What does this RC network do in this audio transformer output stage?
I'm not sure about the purpose of the RC network. It provides a 10k load at frequencies above 16 kHz, and a rising impedance at frequencies below that, becoming an open circuit at DC. It seems rather pointless in this application.

The two resistors at the input of the opamp are used to balance the input bias currents, eliminating one potential source of DC offset in that stage. It isn't clear why the same precaution wasn't taken with the first stage.

It's possible that these are example of "cargo cult" design, in which components get copied from one circuit to another without any real understanding of their purpose.