Consider using a 10k resistor.
The aim is to use whatever is the average resistance of the microphone as it is operating. That's how to obtain maximum voltage swings.
The capacitor blocks DC, so that AC gets to the microcontroller input. However in this case you may get better results if the signal is riding a DC component. It depends on which comes through better: (a) some waveforms climbing above zero V, or (b) all waveforms traversing above and below a midway volt level.
To get sufficient voltage swing, you may still end up needing a pre-amp.