For audio volume control an audio-taper (approximately logarithmic response) pot is desired so that the volume level change with pot rotation gives a perceived linear change in loudness level, due to the logarithmic response of the ear to sound level. Although reasonably common, sometime a audio-taper pot is not readily available, particularly for an odd form factor or dual pot configurations.
One solution to this is to add a single resistor from a linear pot wiper to ground. When sized...