How does this transistor (pre-)amplifier work?
This is not an amplifier. Q1 will clamp the signal at power-on to keep DC from propagating. If the input has +DC on it, the DC will propagate until C10 charges. Q1 will clamp the DC until C11 charges. After C11 charges, there is no base current path and Q1 is effectively out of the circuit. D1 keeps Q1's base from going negative on power-off.