Electronic Music Laboratories, Inc. (EML) 1/3-page ad of its family of products including ElectroComp 101, 200, and 401 semi-modular synthesizers, 300 manual controller, and 400 sequencer from page 37 of Contemporary Keyboard Magazine May/June 1976.
[Update: December 18, 2009 - After this post appeared on MATRIXSYNTH, John Van Eaton posted a response... and it is beautiful!]
This was the second EML ad to appear in CK, two months (one issue) after the initial 1/6-page advertisement appeared in the March/April issue. Gone are the hand-draw fonts, and sadly, that awesome EML logo. Also gone is the 'Stacked' slogan, replaced with the not-so-great "they grow on you...".
On the plus side, the font used underneath the logo is rather funky for its time. Also, the larger space (1/3 of the page area) did let EML include much larger photos of the same gear found in the earlier ad - throwing in a pair of headphones and some patch cords to boot. And they even had room to include one more instrument from their line-up. In the murky depths of the image, on top of the EML 401, is an ElectroComp 300 manual controller.
Trying to find information on the 300 was like pulling teeth. Reference material for most of the EML line is available at Synthmuseum.com and Vintage Synth Explorer (see my first EML blog post for links to instrument pages), but there is relatively little available online for the 300.
I found a good photo of a blue-faced 300, built in 1969, on Sequencer.de (click on the image to enlarge the photo even further), and a photo of a white-faced 300 on OldTech.com.
As far as finding online reference information, there is a bit about the 300's microtonal capabilities on microtonal-synthesis.com but I couldn't dig up much else through quick searches with Google.
So, Mark Vail to the rescue! He describes the 300 in his 'Vintage Synthesizers' book:
"Alternate controller fanatics take note: Along with a few rudimentary synth components, the ElectroComp 300 manual controller offered calculator-type pushbuttons and pitch knobs. According to an EML product brochure, 'The 300 was originally suggested by a professional composer who wanted to escape from the traditional keyboard with its equal temperament and the patterns it suggests.' "An interesting end note: Early issues of Contemporary Keyboard magazine included 'CK Giveaways'. In this issue, CK Giveaway #5 was an EML SynKey. This is probably why this issue of CK also featured a rare full page EML Syn-Key advertisement.