 Janáček's string quartets not only incorporate the tonalities of Czech folk music, they also reflect the rhythms of speech in the Czech language.The end of western tonality, begun subtly by Brahms and made explicit by Debussy, posed a crisis for composers of the 20th century.It was not merely an issue of finding new types of harmonies and melodic systems to replace the diatonic scale that was the basis of western harmony; the whole structure of western music – the relationships between movements and between structural elements within movements – was based on the relationships between different keys.