Article: 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. It also utilized the bassline from Player One's disco record "Space Invaders" (1979). "On and On" is sometimes cited as the 'first house record', though other examples from around that time, such as J.M. Silk's "Music is the Key" (1985), have also been cited.

Now answer this question: what type of bass synthesizer was a staple of the early house sound?
Roland TB-303