Two Soviet scientists, Alexander Shorin in Leningrad (present-day St. Petersburg) and Pavel Tager in Moscow, conducted research through the late 1920s on complementary sound systems, which were ready for use by 1930.
Dva sovjetska znanstvenika, Aleksandr Šorin, u Lenjingradu, i Pavel Tager, u Moskvi, proveli su istraživanje tijekom kasnih 1920-ih o pratećim zvučnim sustavima, koji su bili spremni za uporabu do 1930. g.