assuming what cowmeat means, If you have a synth that is just 1 oscillator, youre gonna have a hard time making the synth fill the frequency spectrum (occupy the bass midrange and treble, not just 1 of them) since its just gonna live in a particular small frequency band. (Obviously you dont have to do that every time but in this particular case it would have probably sounded better.) You can try to turn on more oscillators and lower or up the octave on them to make it sound more full, so you would have multiple oscillators playing their sound at different octaves and with different timbres/soundwaves if you wanted. You can also try to play bass notes with the same synth, or do really big chords but i suspect that won't work very well.

You can also put a lowpass filter on the synth and then automate the frequency at which it cuts off to make the sound less flat, like one of the tracks cowmeat linked has a plucked sound in it iirc and it is probably mostly an envelope that makes the filter initially cut off at a really high frequency and then very quickly it changes to cut off the midrange. Automation is just that, changing the values of parametres over time. You can automate anything pretty much, for example automating the pitch extremely slightly with a sine wave (so that it keeps increasing and decreasing over time) makes synths sound really cute, and all you would use for that is a low frequency oscillator (it makes a parametre change constantly according to a certain wave form) controlling the pitch.