If your talking about analog synthesisers, you can’t really do it without mentioning kit synthesisers and there predecessors the electronic magazine project as I have a particular soft spot for these underrated beasts.
Being into electronic music, synthesisers and having just got into the hobby of home electronics which was later to become a career it was only a matter of time before I was tempted to build my own synthesisers. It wasn’t a long time after synthesisers became commercially available before those industrious geniuses or is that genii, started to publish synthesiser designs in the popular electronic construction magazines of the day.
Elektor was one of the first, they published a design that they called the Formant, it was a modular and first published between 1977 and 1978 .It followed the 1v per octave standard and designed by a certain C Chapman. Being modular it was a very versatile instrument and also because of the 1v per octave standard it was also very interface able and you could build which modules and however many you wanted, the LFO was particularly notable in that it was basically three LFOs in one unit. The filters were also quite versatile in that they could be high-pass, low-pass, band-pass or notch [band reject] they were 12dbs per octave and 24dbs per octave and a non-voltage controlled resonance filter module that was really a glorified parametric equaliser but never the less better to have than not!
Electronics Today International came up with two designs. Maplin the electronic component shop had the 3600 and 4600. These two synthesisers were designed by Trevor Marshall and were published originally in the magazine with the electronic component manufacturer Maplin producing and selling the kits by mail order.One of the prerequisites of this design was that it could be built by anyone with basic electronic construction skills [the original adverts claiming anyone from 15 to 50 could build it] not sure about the upper age limit of 50 though think that might create a lot of controversy nowadays! The 3800 and 4600 were similar machines in terms of circuitry, the 4800 unsurprisingly has more of it though in quantity with an extra oscillator, an extra filter and the thing which to my mind made the 4600 amazingly versatile, the patch panel.
The 3800 takes the route of the Minimoog and most conventional synthesisers since by having things hard wired or by using switches to make some alteration to the reconfiguration of the circuit however the 4600 makes the interconnections by using a square matrix. It had inputs along one side and outputs down the other and by inserting a pin type plug you made interconnections, the equivalent would take masses of switches and loads of wiring and by using this almost unique system it almost had the flexibility of a modular synthesiser. I say almost unique in the fact that the only other synth I have seen this on was the Synthi 100 suitcase synthesiser which had a similar method of patching the modules together.