Kupkovič is one of the few composers to have written a significant amount of music for the accordion. As well as the versions of "Morceau de Genre", he has written "312-SL / 723" (1978) for two accordions, and in 1980 wrote a concerto for the instrument. This concerto was in the later diatonic style which Kupkovič turned to. The harmonies in these later pieces are very simple, and the works have sometimes been compared to Wolfgang Amadeus Mozart. Kupkovič has been extremely prolific in this style.