The 'ratcheting like Tangerine Dream' video on YouTube is mine. I'm happy to discuss the principles used if the explanation on the video isn't clear. I started by making a little passive switch-box to test the principle, then got a couple of Doepfer voltage-controlled switches to confirm it. Of course, you don't need two MAQ sequencers to do it, but the more channels you have to play with, the more control you have over the effect. There must be many other ways to achieve similar effects with Doepfer's sequencer and clock modules, and the COTK Ratchet Sequencer does look very good.
I think one of the other 'ratcheting' videos on YouTube is trying to do it with MIDI instruments. I think this is futile, as you need a CV-and-Gate system to do 'proper' ratcheting. You can of course imitate the effect with MIDI instruments using software sequencers such as Wok's Clockwerk/Ratchit, Numerology, or DIY ensembles in Reaktor.
 
Chris Jenkins