The Doepfer A-198 is a module for your Eurorack unit that allows you to control aspects of your patch with a ribbon controller for a ton of customizable performance options. Some fun applications for the a-198 are controlling pitch and rate, and taking advantage of its pressure sensitivity to increase the volume and depth of effects.
Read more about the Doepfer A-198 Ribbon Controller Module here: https://goo.gl/PxHGoS