Janáček’s spent several years writing his opera "Jenůfa". By the time he was finishing it his daughter had died. Some of his sadness can be felt in the opera. He also worked on a system of speech-melody (making his melodies sound like the rhythm of his language) which was to influence his operas for the rest of his life. "Jenůfa" was very successful when it was first performed in 1904. By this time Janáček was already 50.