The score of Kurt Weill's Zeitoper, Der Zar läßt sich photographieren (1928), is void at its centre: the musical and dramatic climax, the ‘Tango Angèle’, only exists as a gramophone recording, played on stage, while the orchestra falls silent. Just as the perennial themes of love and death are relentlessly updated in this farcical opera into their anti-metaphysical modern-day equivalents – sex and political assassination – so the music avails itself of modern media to bring across its McLuhanesque point: the medium is the message. The sound medium matters in two ways: first, the gramophone emphatically teleports the tango – a fashionable and sexually loaded dance – into the realm of opera; second, the recorded performance constitutes its exclusive musical reality. As if to underscore this point, parts and score of the ‘Tango Angèle’ were lost shortly after Weill produced the recording for the première: only the recording remained. This article reconstructs the nexus between popular music, modern sound media and operatic aesthetics in Weimar Germany: while the recording is an expression of Zeitoper's demand for radical up-to-dateness, the sound of the record, paradoxically, locks it forever in 1928. A relatively obscure work nowadays, Der Zar remains perhaps the most far-reaching response to the Opernkrise of the mid-1920s, reconfigured here as a crisis of musical writing.