This Ableton tutorial clip from the Learn Live series walks through the four multi-stage routing modes inside Roar, Live 12's saturation and coloring device, using a drum loop as the source material. Serial, Parallel, Mid-Side, and Feedback routing are each demonstrated in sequence, making the differences between them easy to compare.
In Serial mode, the output of stage 1 feeds directly into stage 2, letting you stack processing and blend between the two stages. Parallel mode splits the signal so each stage works independently, which is useful when you want to layer a processed version against the dry signal without cumulative coloring.
Mid-Side mode assigns stage 1 to the mid signal and stage 2 to the sides, opening up stereo-specific shaping without touching a dedicated MS encoder. Feedback mode routes the direct signal through stage 1 and the feedback return through stage 2, so stage 2 stays silent until you raise the feedback amount. Syncing the feedback to a tempo value turns that into a rhythmic effect.