Electronic – Gain of this schematic

I am interested in the following compressor, which I reverse-engineered from a pcb (there might be some mistakes, but I don't think so)

(open the schematic in a separate window to see the small text). The lightning sign is +9V DC and Vin is only AC, with frequencies 20 Hz < f < 800 Hz. The chip is a TL074CN quad op-amp, and there's a jfet which says K192A.

I guessed this is a compressor because it makes sense in this application to have one (e.g. make the bass more rich), but I am otherwise clueless as to what this part of the circuit actually does.

I suspect it does amplify the signal a bit, could you tell me how much? I am in principle only interested in the linear range of the compressor, as my point is to bypass it, but I need to match the input and the output's magnitude.
Of course, if you want to tell me exactly what the circuit does, please by all means, go ahead 🙂

EDIT: To clarify: In my previous question (see Short circuit or disconnect to bypass a compressor), I wanted to bypass this compressor. In this question, I am interested in its response, particularly in the linear range.