Pads 3 & 4, Pads 7 & 8, Pads 9 & 10, and Pads 11 & 12 choke already by default because of their shared voices. In fact, there’s no way to turn it off. Even the samples choke the synth voice between those pad, though you can still layer them, but ON the same pad. Usually, I disable those synth engines and load them with samples of my choosing; for example, I like to sample the kick onto Pad 7, then sample open hat onto Pad 8 for a natural gating of those elements. Sometimes I use a closed hat on one track and shaker on the other which can be standard fun with polyrhythms. Luckily, on the MK2 I can sample record any track onto any pad. Hopefully, someone else can chime on the process for the MK1.