The Glagolitic Mass (Czech: Glagolská mše, Church Slavonic: Mša glagolskaja; also called Missa Glagolitica or Slavonic Mass) is a composition for soloists (soprano, contralto, tenor, bass), double chorus, organ and orchestra by Leoš Janáček. The work was completed on 15 October 1926 and premiered by the Brno Arts Society, conducted by Jaroslav Kvapil, in Brno on 5 December 1927. Janáček revised the mass the next year. The Glagolitic Mass is one of the most remarkable and important musical religious works of the twentieth century.