Fuzz Face 20uf

[arfy]

When I got my used Fuzz Face, the 20 uf cap was installed with the negative end to ground, the schematics I've seen show the positive end to ground.  It worked OK but I turned it around and it works OK like that too.  The pedal looks like someone's was changing it around a little inside before I got it.  I'm wondering what that 20 uf cap does and what effect would a value change have.  Does it function like the cathode cap on a 12AX7 stage, boosting frequencies above a certain point?  I would guess you could get rid of a little mud by using a smaller value than 20 uf.  Anyone ever experimented with this?