@LottieVixen Found it ! It's «She's so Disco» by the band Venus on the album «Welcome to the modern dance hall». The «disco» isn't repeated at all in the chorus, there's no riff immediately after but a pattern like the one I described is played by a violin in a different tonality as a kind of bridge somewhere else and the whole thing is… *way crazier* than I even remembered. You can imagine how catchy the tune is if you consider that I hardly ever listen to this album and still felt like dancing on it as if I'd just heard it on the radio.