OK...so in the end, it sounds like you're looking for something more complex than just a typical CV/gate sequencer, something that has some "theory savvy" to it, either in the sequencer itself or via a quantizer setup that can deal with the chordal functions. I would suggest looking at modules along the lines of the Squarp Hermod, Orthogonal's ER-101/102 pair, ACL's Sinfonion, Winter Modular's Eloquencer, Five12's Vector, 1010 Music's Toolbox, The Harvestman's Argos Bleak, or a third-party build of the Ornament and Crimes. Also, pairing this with something along the lines of an external controller that can also sequence or handle chordal duties would be a good idea; check out the very useful Arturia Keystep, Kilpatrick's Carbon, Squarp's Pyramid, Conductive Labs' NDLR, or the Future Retro Zillion.