Audio voltage dimmer trickery! (Potentiometer not working as expected)
Figure 1. Dual slider pot.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 2. Standard wiring.


You should be able to measure the pot's resistance between 1 and 3.
Resistance between 1 and 2 should vary from zero when slider is towards 1 and maximum when slider is at 3.


Using linear taper on audio will result in nearly all the significant volume change occurring in the first 10% of travel. It's usually a terrible idea.