Moog 921A Oscillator Driver/921B Voltage Controlled Oscillator brochure, 1976

Moog 921A Oscillator Driver/921B Voltage Controlled Oscillator four page brochure from 1976.

I knew it had been a while since I last published a blog post, but I didn't realize it has been about a month! Honestly, I have a wack of ads and brochures scanned, but just haven't been able to find the time to find the words. Summer and its ups and downs have gotten in the way a little bit.

But fall is now here! And although its been a pretty rainy one to date, this morning I'm happy to report I'm blogging from my sunny back deck, coffee in hand.

Perfect blogging weather. :)

I've been wanting to start posting this series of Moog module brochures for a while and the 921a/b was an excellent one to start with because there is some great history behind it.

As you may know from previous posts, I'm a big fan of Moog. I'm also an owner of a Modular Moog (see right). Although my modular contains the 901a/b VCO bank - the predecessor to the 921a/b bank - it provides a great back-story to existence of both.

Let's back up a bit. As you can see in my modular's patch diagram (created by Bob Moog himself!), there is both a 901 Voltage Controlled Oscillator as well as the 901 a/b bank that contains one 901a driver that is wired up to control (drive) three 901b VCOs. What's the point of having the 901a/b bank if you could just have 901s?

For a long time I thought the only reasons the 901a/b bank existed was because it was a great way to cram more VCOs into a smaller space. The 901 takes up a lot of room, so getting three or four 901b VCOs with multiple waveforms into the same space really was one convenience of its design. But then I found an even more valuable reason for the a/b driver system a while back when doing some research on my modules.

A PDF article titled "The 901a/b story"  found on synth-werk.com (a company that is building Moog modules!) explains that as the Moog Modular transitioned from a piece of experimental equipment to more of a musical instrument to be found sitting in professional studios and on stage, the 901's thermal instability and older electronic components resulted in problems with tuning. This was fixed to some degree by driving multiple 901b modules from one 901a controller. But, they were still pretty unstable, so Moog eventually replaced the 901 series with the 921 series giving musicians a lot more temperature stability, tracking accuracy and extra functionality.

Great stuff. And so is synth-werks as far I can tell. Definitely going to look into filling that top space in my modular. :)

The brochure/spec sheet is almost as much of a work of art as the 921a/b modules themselves. First and foremost, we get a great close-up of both modules on the front page. Then when you open the brochure up you are greeted with a wealth of knowledge - in fact, pretty much everything you've ever wanted to know about the control panel features and musical applications of the 921a/b. There is even a full page of technical charts and graphs. I'm not even going to pretend I know half of what Moog is talking about there. I'll take their word for it. Finally on the back page we get all the information specs.

I'm a fan of this whole series of module brochures, and you can expect to see more of them soon. But right now its just too nice out. Time to make the most of this gorgeous Sunday.