The Romanian Folk Dances undoubtedly rank amongst Bartok's most popular compositions. The earliest version is scored for Piano (1915) and was published by Universal Edition is 1918. The composer himself orchestrated this version in 1917. Several other chamber music arrangements (for example, Zoltan Szekely's version for Violin and Piano) were not by Bartok, although he authorised them. The musical material derives from Bartok's collections of folk music, which date right back to 1904, when he wrote down a melody sung by a Hungarian peasant girl. In the course of extensive travels throughout Eastern Europe, Bartok compiled an enormous collection of folk tunes (by 1918 his collection comprised no fewer than 2700 Hungarian, 3500 Romanian and 3000 Slovak dances and songs) which would in all probability have been lost had Bartok not written them down. As it was, some of them found their way into his compositions. In 1908 Bartok jotted down tunes in Transylvania. They are the source of Romanian Folk Dances.