Try replacing the leftmost resistor with a 1M pot.
Added: To be a little less terse, the first part of this circuit has the inputs going through 100k resistors to the inverting input of an op amp. The non inverting input is connected to ground and the output feeds back to the inverting input through another 100k resistor:
This is an inverting amplifier whose gain is the ratio of the feedback resistor to the input resistors: 100k/100k = 1. Increasing the feedback resistor would increase the gain. To make the gain variable use a pot wired as a variable resistor:
With a 1M pot the gain varies from 0 to 1M/100k = 10. You could keep the 100k resistor in series with the pot if you wanted to, making the minimum gain 1 on the theory you’d never want to make the drone quieter. In that case the maximum gain would be (100k+1M)/100k. Yes, that amp goes to 11.