Well, I did some checking on my own. Coven has an official web site:
http://www.randycovensite.com
Now I know where I remember him from...the "CPR" album back in 1992 with Al Pitrelli on guitar and Jon O'Reilly on drums.
His latest album is "Witchway." His latest tour was late last year with Yngwie Malmsteen and Dio. His web site has a photo of each of his unusual basses. One is a three octave fretless. You can buy his out of print CDs right at his web site.
It seems to me he used to write a column for bass players in one of the metal guitar magazines like "Guitar World." He has a "Bass Secrets" part to his web site. What I saw was a lesson about using Aeolian and Locrian modes.