I just yesterday uploaded a video in the “latest music” thread in which I route the four outs of my cassette multitracker through my modular.
There is a different chord on every track that drones along. Those four drones go through a pre-amp module to get them to eurorack level and then into the four inputs of planar. So I can blend between the chords with the joystick (plus there goes modulation into the joystick cvs for a constant bit of movement). The the mix out goes through a filter and optomix which is controlled by maths and triggered by meadowphysics.
My multitack isn’t modufied, so there is no cv control. But in this scenario it probably would only mess up the sound.
Edit: Here’s a direct link.