"Great Russian Folk Songs" (published by Professor Alexei Ivanovich Sobolevsky. St. Petersburg, 1895-1902. T. 1-7) - the first in Russian folklore and the most complete scientific set of folk songs. The texts are systematized according to the genre-thematic principle (epics, spiritual verses, ritual and historical songs were not included in the code). The code is composed of printed sources, starting with songbooks (and a few manuscript collections) of the 18th century. A. I. Sobolevsky took care to preserve all known options, including distorted and fragmentary ones (some newest editions for that time were not used in the code). Each volume includes pointers to plots (more precisely, themes and motives), names and a dictionary of local words. The code of A.I. Sobolevsky to this day remains unsurpassed in scale and level of systematization by the scientific source of classical song folklore.