If musical folkloristics is also in close connection with the group of social and economic sciences - in so far as it, like all other musical sciences, reflects the process of social development, the historical illumination of folklore phenomena and facts and especially the historical periodization of these phenomena in the present state of this science encounters very great, not to say insurmountable, difficulties. And most of the attempts to "historicize" folk-music creation, many of the efforts to periodize folk-music phenomena degenerate due to the lack of concrete data, in some mechanical constructions, in abstract theorizations, nonspeak and historical formalism. 

The historical elaboration and especially the periodization of folklore material are hampered by the fact that in the same folk song there are elements, layers (interferences) from different epochs, different authors, different styles, different genres.

The observations of folklore collectors show that different, distinct artistic manners, styles and schools can be revealed in the singing of songs, the telling of tales and the performance of customs, each of which has its own traditions and whose traditions are often lost in the distance of the past. This further complicates the question of the historical treatment and periodization of folk-song material.

If the periodization of folk phenomena is so difficult in folk poetry, in whose lyrics some historical event, some personality, or some feat has nevertheless been reflected, how much more difficult, not to say impossible, does it prove in folk music, where the folklorist operates not with concrete historical data but only with musical images. Here the work of the researcher is further hampered by the following circumstances:

  1. The lyrics of a song may allude to some event which took place immediately before the song was written; but it may refer to events which took place many years, even many centuries, before the song was written. Soldiers even today compose songs about the conversion of the Bulgarians, the Samuil wars, etc., under the impression of what they have heard or read from Bulgarian history.
  2. The most ordinary phenomenon in folklore is the superimposition and adapting of old texts on old melodies and vice versa. Everybody knows how many melodies are sung over the lyrics of the song. Different lyrics to the same melody or different melodies to the same poetic text can come from different historical periods. Which of these periods should we take as the period of the origin of the song when we carry out the periodization?
  3. The verbal texts of many folk songs have been forgotten and today these songs exist only as instrumental melodies . In such melodies there are no specific indications of persons, places and events by which the periodization could be carried out.
  4. The songs undergo continuous changes. They are subject to a long evolution, they are not created in a complete form but only schematically. According to the modern conception of the most eminent folklorists, the 'bearer', i.e. the performer of a folk song, is also its author: he more or less modifies it by improvising on its basic theme. The song, therefore, reflects most strongly not the epoch referred to in its text, but the epoch of the 'bearer' (the so-called informant). The rest of it is a relic. But our sheet music records only date back a few decades.

While noting that the researcher of musical folklore encounters many great difficulties in the historical illumination and periodization of folk melodies, we do not mean to imply that all periodization is superfluous, useless, and that the scholar should abandon it altogether. He will have to proceed to a scientific treatment of the folklore material with a view to a preliminary arrangement of it by periods.

Of course, until specific historical data and evidence for each song are gathered, this arrangement can be made only in the most general terms and only approximately, paying attention to the era, the historical events and the persons alluded to in the poetic text.