> Does the A-137 Wave Multiplier also rectify somewhat, via the
> "Symmetry" setting, or am I understanding it wrong

Yes, it does. The waveform is 'folded' about two levels, the sum and
difference of the 'symmetry' and 'folding' settings, and this folding
is essentially 'rectification'. This 'rectified' signal is then
multiplied by a gain determined by the 'harmonics' setting, and mixed
back into itself: this whole process is then repeated four times, so
that what comes out at the end looks nothing like rectification at all.

Both the A-136 and A-137 I feel are difficult modules to get grips
with: even knowing how the circuits work from the schematics, it is
difficult to abstract to simpler levels and summarize what they do. The
alternative method is not to worry about this, and just listen to what
they sound like, and decide what works for you, and what doesn't!

Tim