The historical performance «The early Reign of Oleg» written by Catherine II and staged as a semi-opera in 1790 can be regarded a part of Catherine’s ambitious «Greek project» ideologically rooted in the old concept of Moscow reign (and the Russian empire in general) as the «Third Rome», the heir of both the ancient Greece and Byzantium. Giuseppe Sarti, the Prince Potyomkin’s maestro di cappella, was personally commissioned by the Empress to compose music for the last act of the play which contained a vast quotation from Euripides «Alkestis». The unusual task provoked the unique attempt of reconstructing the ancient theatre with genuine text (in Russian translation) and the music in «Greek» modes, containing also a melody from Pyndar’s ode, published by Athanasius Kircher in 1650 and regarded in those times as authentic. Sarti wrote not only the music, but also an «Explanation» describing his efforts to compose the Euripidean episode in the «Greek» taste. Although the modality of Sarti’s music can be disputed today as dubious, his experiment surpassed even Gluck’s reform operas and found no equivalents in contemporary music.