Stalin's death in 1953 allowed a certain relaxation of the cultural totalitarianism in Russia and its satellite states. By 1956, political events had led to a partial thawing of the musical climate, and the Warsaw Autumn Festival of Contemporary Music was founded. Conceived as a biennial festival, it has been held annually ever since 1958 (except under Martial law in 1982 when, in protest, the ZKP refused to organise it). The first performance of his "Musique funèbre" (in Polish, "Muzyka żałobna", English "Funereal Music" or "Music of Mourning") took place in 1958. It was written to commemorate the 10th anniversary of the death of Béla Bartók, but took the composer four years to complete. This work brought international recognition, and the annual ZKP prize and the International Rostrum of Composers prize in 1959. Lutosławski's harmonic and contrapuntal thinking were developed in this work, and in the "Five songs" of 1956–57, as he introduced his twelve-note system, the fruits of many years of thought and experiment. He established another feature of his compositional technique, which became a Lutosławski signature, when he began introducing randomness into the exact synchronisation of various parts of the musical ensemble in "Jeux vénitiens" ("Venetian games"). These harmonic and temporal techniques became part of every subsequent work, and integral to his style.