Stereo Automation?

[David White <whitedavidp@xxxxxxxxxxx>]

One of my buddies wants to build a remote control mechanism to turn the
volume control on his stereo. He imagines some kind of motor or servo
from an RC application that is somehow linked to a pulley which connects
to the volume knob with a rubber band or the like. It obviously needs to
move slow and steady yet it need not move a huge distance (if geared
properly). He doesn't want to use a huge RC radio to control it though.
He wants something much smaller. Any ideas? He knows that there are
boxes that can be added to a stereo that are essentially remote control
volume devices but he is an audiophile and wants to add nothing to his
system that might dirty the sound.