This paper uses the general framework of the Strong Program to analyse popular music criticism and reconstruct the cultural codes of Stalinism in Czechoslovakia (1948–1953). I focus on the ambiguous place of jazz music, challenging the conventional narrative that Stalinists rejected jazz on political grounds. Building on Kurakin’s work on the impure sacred (2015) and integrating it with the Strong Program perspective on music, I argue that, at the height of Stalinism, jazz held an uncertain position between purity and pollution. While some critics argued that it was the music of the oppressed black American proletariat, hard-line Stalinists treated it as a profane, imperialist influence and a moral hazard. I suggest that the distinction between the sacred and the profane is not always self-evident to actors, triggering intense processes of symbolic and performative negotiation. This uncertainty resulted in the regime’s ambiguous policies towards jazz.