This text deals with Leoš Janáček’s essay Brezovská píseň (Folksong in Brezová, 1899), which was not published during the author’s lifetime. In it, he described his visit to Březová. The notations of folk songs made on this occasion as an organic component of Janáček’s text were previously regarded as lost, and only a selection from them was later arranged and included in his treatise O hudební stránce národních písní moravských (On Musical Aspects of Moravian Folk Songs, 1901). It is now possible to supplement the original essay Brezovská píseň with all of the musical examples, for which originals and copies of long-drawn-out songs and dance songs are available. The newly discovered sources allow a comparison of the descriptive and prescriptive treatment of long-drawn-out songs, to which the composer attracted attention as the first observer with expert training, thereby arousing the interest of future generations of scholars to the given topic.