The article is devoted to the problem of cultural traditions and cultural heritage associated with St. Petersburg and its importance in the culture of Russia. It explores the musical world of the greatest composer of the XX-XXI centuries. Sergei Mikhailovich Slonimsky, a native of St. Petersburg, in whose work and all extensive activities the city on the Neva played a decisive role, becoming a kind of cultural code of his artistic life. These features manifested themselves in the family genetics of the Slonimsky clan, the years of study and work associated with the St. Petersburg Conservatory, in an organic fusion of Westernizing and Slavophil tendencies typical for the culture of St. Petersburg, on the basis of which the musical image of St. Petersburg (Petrograd, Leningrad) was formed in his work. The conclusion is made about the deep national originality of the musical world of Slonimsky, formed by the universal “code of Petersburg” and which has become a precious heritage of Russian, European and world cultures.