Many years ago I was religiously subscribed to Keyboard Magazine, then called Contemporary Keyboard (and bi-monthly) and I still have Vol. 1 Number 1 September/October 1975 issue (article on Chick Corea and NAMM 1975) as well as several other older issues I considered important.
At one time it was the only magazine geared for keyboardists, and in much later issues they even started reviewing Arranger Keyboards such as the Korg SAS-20 and Yamaha PSR-70 around 1983/1985, but mainly it was synthesizers and electric pianos.
There were also some great tutorials and some excellent interviews with the leading players at the time...I remember a Jimmy Smith interview that was very interesting...he used to use an old Cadillac hearse to haul around his old Hammond B-3 and he explained his use of bass pedals in conjunction with Left Hand bass.
I do remember seeing the first mention (showed at NAMM) of the Moog Polymoog (model 203a) in that first 1975 issue and knew I had to get one, as most synths available at the time were monophonic, whereas the Polymoog was fully polyphonic and had 71-note weighted Pratt & Reed touch-sensitive (velocity) keyboard divided into three sections with a volume slider for each.
Having that keyboard got me a lot of studio work, although initially, it wasn't a very reliable instrument until I had an electronic wizard friend of mine do some custom mods to it.
So, back then, the magazine was invaluable to many of us.
Nowadays, I only view Keyboard Magazine on-line....I believe a subscription for print, digital and iPad versions are available at the web site.
http://www.keyboardmag.com/Ian