Järnefelt made his living primarily as an opera conductor. Around the turn of the century, however, he also had serious plans to compose an opera which was to be based on a Finnish version of a medieval English ballad, and was to be called Velisurmaaja Later, at the beginning of the 1910s, it was suggested that he write an opera based on Juhani Aho´s novel Juha, but he refrained.
Järnefelt never came to write an opera, but incidental music on the other hand was a familiar genre for him. All in all, he wrote the music to four plays. In Finland, he wrote the supplemental music to the performance of Miranda based on Topelius’s saga (1901), to Immi Hellén’s biblical drama Luvattu maa (1907), and to his brother Arvid’s play Titus (1910); in Sweden he composed the music to a production of Aristophanes’ Fåglarna in 1928.
For these plays, Järnefelt wrote musical interludes, songs, and melodramas (spoken text with background music). Stylistically, the individual pieces embody an extensive scale with regards to the demands of changing events on stage. Concert audiences are, above all, familiar with the three-movement suite from Luvattu maa which ranks among his grandest conceptions, and can even parallel the suites from Sibelius´s incidental music.
Similar to the incidental music is the music to the epic 1911 film Sången om den eldröda blomman, a film by the distinguished Finnish-Swedish director Mauritz Stiller, based on the bestselling novel by Johannes Linnankoski. The film would become the sprouting Swedish silent film industry’s biggest success to date. It is considered ground-breaking within the Nordic Film Industry; the first Nordic feature film to which an original sound track was composed. The Finnish subject matter lead Järnefelt toward the National-Romantic style, however the breadth of expression ranges from tender lyricism to breathtaking drama. From this film music, the best known is from the roaring-rapids daredevil scene, from which Järnefelt made an orchestral version called Koskenlasku.