Bottom = Rat = variable low pass filter
Middle = Muff = a low pass filter and a high pass filter combined
Top = variable high pass filter
Basically a Muff tone control is a low-pass filter and a high-pass filter combined, so in the cleric the two filters are individually hooked to the on/on/on switch. It turns them both on in the middle, then only one or the other in the other two positions (a genuinely cool trick from JPTRFX that I haven’t seen elsewhere but would love to be better informed if I’m incorrect)
I love the high pass filter on the OG pedal (go-to mode of the three), it lets you tighten the bass and/or get *super* sharp and aggressive