Parallel RC as a filter?
It looks like a first-order passive high-pass shelving filter.

Its role is to attenuate low-frequency content of the audio signal without cutting it off. Mainly used to reduce (de-emphasize) excessive bass as a form of coarse equalization via bass-trebble (tone) controls.

Some features:


Attenuation of low-frequency content is: \$\alpha = 20 \log \big(1+\frac{R_1}{R_2}\big)\$. In this case approx 5 dB attenuation.
Attenuation of high-frequency content is 0 dB. 
There is a transition band in-between that goes from \$f_z = \frac{1}{2\pi R_1 C_1}\$ to \$f_p = \frac{1}{2\pi (R_1 || R_2) C_1}\$, which are the frequencies where the zero and the pole of the transfer function of the filter are located. In this case, transition goes from 1,205 Hz to 3,617 Hz.


There are active and higher order variants of the high-pass shelving filter that allows you steeper transition bands if you need them, and also help avoiding loading effects.