a low-class urban music. This changed in the 1930s, when the rising Indonesian film industry began incorporating kroncong. And then even more so in the mid- to late 1940s, it became associated with the struggle for independence. Perhaps the most famous song in the kroncong style is "Bengawan Solo", written in 1940 by Gesang Martohartono, a Solonese musician. Written during the Japanese Imperial Army occupation of the island in World War II, the song (about the Bengawan Solo River, Java's longest and most important river) became widely popular among the Javanese, and then later nationally when recordings were broadcast over the local radio stations. The song also became quite popular with the Japanese soldiers, and when they returned to Japan at the end of the war re-recordings of it (by Japanese artists) became best-sellers. Over the years it has been re-released many times by notable artists, mainly within Asia but also beyond (like Anneke Grönloh), and in some places it is seen as typifying Indonesian music. Gesang himself remains the most renowned exponent of the style, which although it is seen now as a somewhat starchy and "dated" form is still popular among large segments of the population, particularly the older generation. After World War II and during Indonesian National Revolution (1945–1949) and afterwards, kroncong was associated with patriotism, since many of Indonesian poets and patriotic songs authors uses kroncong and somewhat jazz fusion as the genre of their works. The patriotic theme and romantic wartime romance was obvious in the works of Ismail Marzuki, such as "Rayuan Pulau Kelapa", "Indonesia Pusaka", "Sepasang Mata Bola", "Keroncong Serenata" and "Juwita Malam". These patriotic songs can be sung in hymn or even in orchestra, but most often was sung in kroncong style known as kroncong perjuangan (struggle kroncong). The kroncong divas; Waldjinah, Sundari Sukoco and Hetty Koes Endang, was instrumental in reviving the style in the 1980s. Langgam Jawa There is a style of kroncong native to Surakarta (Solo) called langgam jawa, which fuses kroncong with the gamelan seven-note scale. Gambang kromong Early in the 20th century, kroncong was used in a type of theatre called Komedi Stambul; adapted for this purpose, the music was called gambang kromong. Gambang kromong is quite prevalent in Betawi culture of Jakarta. Tanjidor Tanjidor is a traditional Betawi musical ensemble of Jakarta. The instruments used are almost the same as a military marching band and/or corps