The hypnotic electronic dance song "On and On", produced in 1984 by Chicago DJ Jesse Saunders and co-written by Vince Lawrence, had elements that became staples of the early house sound, such as the Roland TB-303 bass synthesizer and minimal vocals as well as a Roland (specifically TR-808) drum machine and Korg (specifically Poly-61) synthesizer. What type of bass synthesizer was a staple of the early Sanders sound