While the built-in effects of the OB-6 are great... for me, they fell short for in the reverb area. I've wanted a 'real' reverb unit for a long while now, and a couple of videos recently convinced me to give the Strymon BigSky a trry. So a couple of weeks ago I picked one up through Sweetwater... yikes. What a difference for pads / strings / ambient stuff. They are pricey, but there's a good reason for that. It is loaded, with multiple 'reverb machines' - each with unique settings / effects to what youre sending through it. There's plenty written up about the BigSky .. so I'm not reviewing it per se - but mostly posted, to say... it augments the OB in an incredible way.
The first unit I was sent, was DOA. Sweetwater sent out a replacement system, which I received a few days later, along with mailing packaging / routing for the return. Was really a pain-free transaction, and two thumbs up for Sweetwater's service.
I routed the BigSky on an Aux send from my mixer, and have used it with everything I have. It's really a fantastic unit, and though I am still learning my way around it - it's pretty easy to hone in on effects / timbres that you're looking for. Anyway -- highly recommend, if you're looking to sweeten up the sound of your OB-6 or other gear.. give the Strymon BigSky a look.
Here is the video that initial sold me on the BigSky. Of Note: It took about 2 minutes to dial in the patch, on both the Strymon and the OB-6. Seriously ... easily done. I used a string-brass patch I had on my OB, and lengthened the attack / decay... and modified a BigSky 'Sloud' reverb machine to match.
https://www.youtube.com/watch?v=lNA5PSOlV7U Also - there's a Peter Dyer - Strymon BigSky Reverb synth demo on YouTube.. that I used for inspiration (and it gives you a good idea of other keyboard-related timbre-altering reverbs you can get out of the BigSky.
Joe (no affiliation with Strymon . . . just passing on my opinion )