The word has also been used as the title for short pieces of music, typically for the piano. The best known bagatelles are probably those by Ludwig van Beethoven, who wrote three sets, opus 33, opus 119 and opus 126. Other notable examples are Franz Liszt's "Bagatelle sans tonalité" (an early exploration into atonality) and the set of fourteen, opus six, by Béla Bartók. Anton Webern wrote a set of six for string quartet (opus nine).