OK, so I got to thinking that while I often note that users should study up on some of the classic monosynths that have stood the test of time, I haven't really given a lot in the way of examples to specifically look at. So this post is designed to correct that omission. All of this fun stuff can be found on and referred to at Vintage Synth Explorer (http://www.vintagesynth.com/#synth-models), which is a pretty good reference site for prebuilt synths, including some of the preconfigured modular gear of bygone times. You could kill hours on this site easily...but I guarantee you'll come back to MG with a head full of ideas as a result. Let's hit the high points, though...
These synthesizers are ones which I'd like to point out as being classic instruments which also go quite a way to explaining both how a proper synthesis signal path should flow. Also, their configuration gives some very good suggestions as to how to lay out a modular cabinet in such a way as to get the result to have an 'instrument feel'. There are very good reasons why some of these command big money prices on the used market and, in fact, why a few are still in production to this day. None of these are modulars per se, but a number are patchable and can be inserted into a modular setup. But again, the point here isn't the modular aspect, but how you can look at classics such as these as a 'roadmap' for your own modular efforts. The ones to pay attention to are:
1) ARP 2600. This is actually halfway in between a modular and a prebuilt, since the patchable architecture was always intended as a 'convenience', with some submodules not patched into that but easily configured via patchpoints. Also, it's worth noting that other devices were created that act essentially as 'modules' that connect to the 2600, such as ARP's 1604 sequencer and Tom Oberheim's initial synth effort, the SEM.
2) ARP Odyssey. Technically still in production thanks to Korg, this was probably the best non-patchable monosynth that ARP came up with. It had duophonic architecture, and the panel layout was (along with the Minimoog) influential in the designs of many monosynths that followed.
3) EML 101 'ElectroComp'. In some ways similar to the ARP 2600, this and its separate modular expander, the EML 200, are still devices that turn up in educational studios to teach the fundamentals of synthesis. The panel shows the flowpath exactly like a road map, so it's hard to misunderstand how the various subsystems go together...which also makes it a good example for the flowpath for present-day modular design as well.
4) Korg MS-10 and MS-20. The latter, of course, is another reissue in its 'mini' form by Korg...and rightfully so, since it's probably one of the most capable small monosynths ever made. These two monosynths, with the 10 being a simplified 20, also make use of patchpanels to override the built-in patch architecture as well as to patch in a number of other MS-line devices. And again, the way that Korg laid these synths out provides a great example of how 'flow' should work. After all, the MS-20 dates from the late 1970s, and it still sells bigtime given how it can be used for both very basic duty and very extreme uses. I would even go so far as to call it the 'Japanese ARP 2600', because in some very real senses, it's that.
5) Moog Minimoog. The first of the 'lead synths', really, this was originally derived by Moog engineer Bill Hemseth from Moog's modular line in its prototype form. Bob Moog actually didn't like the idea of this machine, but came to see the potential that it had in the end. The layout was derived as something of an extremely scaled-down signal flow version of the Moog IIc, with a reduction in VCOs but still retaining Moog's classic 904A low-pass filter. Numerous Moog monosynths begin their lineage from this synth, including the Micromoog, Multimoog, and Prodigy, as well as the more recent Voyager. And of course, it's worth noting that Moog has brought this specific 50 year old synth design back more recently still...because, simply put, it works.
6) Roland SH-1 (and its offshoots, the SH-09, SH-2a, and the later SH-101). Another line that will not die, the SH monosynths were a basic working tool of many a synthpop player in the late 1970s and up through the development of techno and on into the rave scene of the 1990s. And yet again, it's because they make simple, straightforward sense. You would have to really try hard to make a mistake programming these. And yes, they still linger on, with a VCM model version of the SH-1 available for Roland's present-day System synths, and the SH-01 being a redux of the venerable 101 with a bit of the related MC-202 thrown in for good measure.
7) Sequential Circuits Pro-One. A monosynth based on the Prophet-5's CEM-based architecture, this powerful monosynth yet again boasts an excellent and intuitive flowpath on its front panel, plus the complexity of the modulation matrix. This is something that I think everyone wishes Dave Smith would reissue just as it was, because it remains a very sought-after monosynth...great sound, intuitive programming environment.
8) Yamaha CS-monosynths (CS-5, 10, 15). These bear some basic resemblance to the Korg MS-series in sound and appearance, but not in implementation. These probably have some of the best road-mapping of monophonic synth architecture, especially the CS-15 with its flowpath showing how to use it in either monophonic or duophonic modes via a bit of extra patching. I would go so far as to say that the CS-10 or CS-15 might be some of the best 'explainers' as to how an analog synth signal path gets put together.
OK...so there's a few there that I think are perhaps the best 'study pieces' for anyone stepping up to the task of designing a modular in any format (well, except maybe a Buchla or Serge). And better still, if any of you reading about these can find some of the actual devices to check out, hands-on. Any of these serve as an excellent template to build up a rackful of modules, because following these fixed-build synths will help you to cook up a modular rig that both has what you need AND has a layout that is intuitive and possesses some of the same characteristics of playability that keep them in the 'very desireable' column for many electronic musicians. So...class dismissed! Study well, o my droogies...