OT: Pedal unity gain mod question

[Tim Nelson <tnelson@metrocast.net>]

Sorry for the off-topickedness, but would anyone happen to know a simple
mod that would allow me to turn a pedal's 'drive' pot lower than zero?

Specifically, the pedal is a cheapo Danelectro 'Rocky Road' Leslie
simulator, which (much to my disbelief) actually sounds quite good, but the
volume difference between 'off' and 'on' is driving me nuts. I've got the
'drive' control all the way counterclockwise, but it needs more 
attenuation.

Would a resistor added to the pot's output do it? If so, what value would
be a typical starting point for such an application?

-t