This sort of “fake pizzicato” synth sound is a disco classic, many others before Siriusmo have used it. Most notably, Massara’s Margherita (later covered by Boney M.) makes thorough use of this sound, and many of Perrey and Kinsgsley’s songs also feature it (by the way, Siriusmo himself has sampled Perrey a few times).
It’s a simple sound to get “in the ball park”, but to make it sound great the details are important. It has obviously a short attack in both filter and vca envelopes, and a short release. Play with your adsr controls to get it right.
To get the best results send a generous amount of envelope modulation to the filter, and use two vcos sync’d selecting the pulse waveforms. The key is to get a very narrow square wave (moving the pulse width controls) and playing with the pitches of the sync’d oscillators to get the right high frequency content.
Last but not least, to achieve the trademark Siriusmo sound it’s advisable to use plugin-style brickwall limiters, some reverb and a highpass filter before hitting the limiter