In his article Hungarian Peasant Music, Béla Bartók writes:1
Among the melodies employed by Liszt in his Hungarian Rhapsodies, and by Brahms in his Hungarian Dances, there are scarcely four or five genuine peasant melodies, and
even these appear in a much distorted, "Gypsy-like" form. All the remainder are art-
melodies in folk-music style. For the programs of the Gypsy musicians are made up
chiefly of such melodies, sparsely interspersed with real peasant tunes; these musicians
adapt both sorts of melodies to their own taste. For instance, they imported the step
of an augmented second (with which we are familiar in the so-called "Hungarian scale,"
but which is never found in the Hungarian peasant melodies) from the melodies) from the Balkans, or still further away, into the Hungarian art-music in folk-music style.2
Further on, Bartók gives two examples.
T: From "Hungarian Peasant Music" by Béla Bartók
GGgg | ga g2 | f2 fg"//"x | aaag | de f2 | d2 dd"//"x | gccc | cd c2 | B2 Bc"//"x | dddc | GA B2 | G2 GG || &
cBcd | e2 d2 | gg f2"//"x | cBcd | e2 d2 | cc B2"//"x | GAGF | G2 F2 | dc B2"//"x | GAGF | G2 c2 | GG G2 ||
These two airs were utilized in Liszt's Thirteenth Hungarian
Rhapsody; No. 11 is the first theme of the Allegro section, much
distorted by graces and figurations in Gypsy style. (On closer
scrutiny of these figurations it is evident that their origin can be
traced to the West-European art-music of the eighteenth century.)
No. 12 is the second theme of the Allegro section; in the Liszt
melody, the close, in particular, shows a deviation from the
original peasant form; it closes a third lower than our example.3
On the other hand, in "A study of Franz Liszt’s Hungarian Rhapsodies"4, Dana Charlene Francey writes:
The second chapter of the thesis will describe the relationship of the Hungarian Rhapsodies with the original collections of Hungarian folk tunes on which they are based (Macwar Dallok and Macwar Rhapszodiák pieces), and subsequently will use the relationship with this pre-existing material as the foundation for grouping them into categories, e.g., Hungarian Rhapsody Nos. 1-2 (based on folk tunes not found in the Magyar collection); Hungarian Rhapsody Nos. 3-15 (based on folk tunes found in the Magyar collection); Hungarian Rhapsody Nos. 16-18 (not based on any pre—existing material —- all original works); and Hungarian Rhapsody No. 19 (based entirely on Csárdás nobles by Abrányi, an Hungarian composer).5
The dissertation gives an extensive analysis of the source material for the Hungarian Rhapsodies.
1Bartók, Béla (trans. Theodore Baker). "Hungarian Peasant Music." The Musical Quarterly 19, no. 3 (1933): 267-87. Accessed September 21, 2020. http://www.jstor.org/stable/739077.
4Francey, Dana Charlene. 1992. “A Study of Franz Liszt’s Hungarian Rhapsodies.” Retrospective Theses and Dissertations, 1919-2007. T, University of British Columbia. doi:http://dx.doi.org/10.14288/1.0086785.