> I'm new to Modular synthesis and I'm trying to find articles that
> explain how Modular synthesis works but I haven't really found
> anything so far on the web.
>
> I understand the basics of sending voltages to play notes but I'm
> interested in learning about how Modules like the Doepfer A-160 &
> A-161 work and basic sequencing in modular synths.

No one mentioned Sound on Sound's Synth Secrets articles from a few
years ago

http://www.soundonsound.com/sos/allsynthsecrets.htm

They are listed in order from last to first, so you would want to
start at the bottom and work your way up.

Though I think what you are trying to learn about is more specific
than general after reading your original question. Because the
Doepfer modules constitute a very basic but uncommon toolset it's not
going to be directly covered by a general book.

The A-160 and A-161 take in my opinion a very back to the most basic
approach to a sequencer. I would think the Doepfer manuals would be
the primary info on those modules. The name sequencer comes from the
term sequential switch which is telling. The A-155 is far more the
developed classic sequencer design but the basis is a device that
sends out different triggers/gates in sequence.

The idea with the A-161 is you have 5v is coming out of each output
in order. The "trick" to make it a sequencer, as most people use the
term, comes by attaching each output to one mixer module. It will
allow you to change the 5v to some other value you can use for pitch
of a vco and combine all the stages into one varying output (rather
than 8 identical ones) that you can connect to your VCO(s).

Just manually adjusting the mixer will probably produce pitches in-
between scale notes. You could try to use reference audio tones from
another tuned keyboard and adjust to match by ear or you could get a
quantitizer module to round the output to a note of the standard
scale. Also a regular Doepfer mixer doesn't have 8 inputs. You could
either connect the last stage you want on the A-161 to the clock
reset on the A-160 to get less than 8 sequencing stages or you could
do something like get a mix expander module for 9 inputs. But still,
it's worth emphasizing that a more typical classic sequencer is the
A-155 while in my opinion, the A-160 and A-161 are "back to basics"
tools to create more complex patches and use for other triggering
needs when you want different triggers out of a uniform clock import.

Nick