100uf Capacitor in Big Muff

[playpunk]

Hey, did you know that this thing still works if you leave off this cap? I did, accidentally, and mine still worked. It wasn't very loud, but it worked.

Why? Is the electrolytic just a power-filtering cap, or does it have some other function?

[Guitarmageddon]

If there's a 100uf cap in a Muff it'll be to filter the power supply. It shouldn't have any effect on the effect volume.

[Clayford]

Is the electrolytic just a power-filtering cap, or...

Correct. Worth mentioning that it didn't exist in the first few iterations of the BMP that were battery only.
If your Muff is not very loud, you need to double check things as there's a fault in your circuit.

[chromesphere]

^ what they said.  You may find there is extra noise in your big muff without the cap.  Which actually, most the big muffs I've built are quite noisey, even on a regulatored PSU.