The cash register in question is an AKAI MPC-60 MK 2. It's 12 bit and uses floppy disks. Two of them are being played live. The MPC 60 and the MPC 3000 were designed by Roger Linn and bear little resemblance to their weak progeny (not designed by roger linn): 2000, 3000, 1000, 4000, 2500...