I would agree with tek's reply ... DX7

Even though there were other systems around at this time they were only low resolution samples and weren't really suitable for pushing up front in a mix like this sort of bassline. Great for background pads, drums and breathy sounds which would hide the sound problems of early sampling. I used a Fairlight CMI MK1 in a studio and found that trying to use it as a featured pitched instrument was a problem. The lores samples paled next to real instrument recordings and attempts to EQ them to provide better dynamics simply made the digital problems more prominent. The DX7 although being early digital still produced a punchy sound through its 12bit DACs and its slap bass sound drove many early 80s hit songs and TV themes.