I just got the Schlappi Engineering Angle Grinder and 100 Grit which can make some crazy types of drones for days especially when you feed different types of CV and sequence them. In fact, just using the 100 Grit came up with weird drones tonite of all types. As others mention, Noise Engineering makes great modules for this like Cursus Iteritas which I feed into Mimeophon for drones on days.