The government emphasized optimistic folk-based tunes and revolutionary music throughout most of the 20th century. Ideological messages are conveyed through massive orchestral pieces like the "Five Great Revolutionary Operas" based on traditional Korean ''ch'angguk''. Revolutionary operas differ from their Western counterparts by adding traditional instruments to the orchestra and avoiding recitative segments. ''Sea of Blood'' is the most widely performed of the Five Great Operas: since its premiere in 1971, it has been played over 1,500 times, and its 2010 tour in China was a major success. Western classical music by Brahms, Tchaikovsky, Stravinsky and other composers is performed both by the State Symphony Orchestra and student orchestras.