Dissecting/Analyzing an audio amplifier

[ajcrm125]

It's been years since I messed around with analog stuff (my day-to-day job is a digital designer) but I'm working on an arcade game and want to better understand how the audio circuitry is laid out. Specifically the opamps and surrounding circuitry.
Attached is the circuit for reference. For now, all I care about is everything to the right of the yellow line.



So let me explain what I 'think' I know and you guys can correct me and/or fill in the missing pieces.

The source signal DAO passes though C32 and R51 to an inverting amplifier implemented by one of the opamp's at 2N. I'm assuming C32 is to create a highpass filter?
That amplfier has a gain of -1.2 due to R52 and R51. The output should be centered around 1/2 the opamp's power supply voltage because of the voltage divider created by R53 and R54.  Not sure what C30 is for other than to reduce noise on the non-inverting input?
R55 and C39 is used for a lowpass filter, and it looks like the other opamp at 2N is being used as a buffer so I'm not sure what R56, R57, C41 and C40 are used for.
Finally we have another highpass filter at C42 (?) and a final amplfier using Q1 (which I am less interested in than that opamp stuff).

Thanks for any info!
-Adam

[Kleinstein]

The last OP and the circuit part from C39,C40,C41 forms a 3rd order active low pass filter. The configuration is called Sallen key
https://en.wikipedia.org/wiki/Sallen%E2%80%93Key_topology

The high pass fitlers are more like coupling capacitors to get rid of DC offsets, not really filtering in the actual audio band.

Audio with an LM324 OP amp is not really high quality - it is normally an OP to avoid for audio use as it produces quite some cross over distortion.