|I see Marv, that makes sense. The extra resistance then may be getting used as an offset / voltage divider to the main pot. I found 40 and 50% "loudness tap" pots after searching the net.
Steve - If you just connect an ohmmeter btwn each of the different terminals as you adjust the pot, you will know what they are doing and be able to replace that functionality. If part of it remains fixed, then it could probably be replaced by a fixed resistor in series.
As Lewis noted, knowing the model number would help. Then, we should be able to check the schematic and see what the circuit looks like.