In the past I have had a tube of gooey black stuff in a tube called
"Belt Grip" that really made flat belts work well (quiet, no slip).
I now seem to have a selection of spray cans of tacky stuff that makes
a mess, makes a "squitch" noise as the belt comes off the pulleys, and
then quits working a day later.

Does anyone know where to get some of the old tar and rosin mix or
whatever it is/was?

Thanks,
Alan Erb