The Eight Improvisations on Hungarian Peasant Songs for piano marked a significant moment in Bartók's oeuvre, the point at which he began to treat folk tunes as malleable musical material. Instead of taking a simple folk tune and harmonizing it, Bartók was now manipulating the folk tunes, transforming and shaping them to fit his compositional needs while still retaining their original spirit. Folk music is at the heart of nearly all of Bartók's compositions, beginning with his works at the end of the first decade of the twentieth century. By this point, Bartók had spent several years collecting folk tunes from all over Eastern Europe. For Bartók, folk music served as raw material for composing art music, and indeed the musical idioms of Hungarian, Romanian, and Slovakian folk music became a fundamental part of Bartók's compositional style. These Improvisations show Bartók realizing, perhaps for the first time, the true fecundity of the folk music he had come to know so well.
The first Improvisation is a very simple setting of the original melody, with very little variation of the tune, which is repeated three times, followed by a coda. The melody is modal, derived from the C Dorian mode. It is the harmony that is most interesting as it varies between diads, triads derived from the melody notes, and triads harmonically unrelated to the melody. The second Improvisation is more fragmented than its predecessor, with its syncopated rhythms and sudden tempo changes. Though it shares the C Dorian mode with the first Improvisation, the melody of the second also contains mixolydian mode fragments, and is much more dissonant than the first. The third Improvisation is polytonal, and quasi-pastoral in character. The fourth Improvisation is quick, and features ostinati. It is followed by the pentatonic fifth Improvisation, which includes the use of canonic imitation (a favorite technique of Bartók's) and polytonal harmonies. The sixth Improvisation is also pentatonic, but with a bitonal schism: the folk melody is played on the black keys of the piano, which comprise a pentatonic scale, while the accompaniment is played on the white keys, thus creating a harsh bitonal harmonic relationship between the parts. The seventh Improvisation includes the technique of mirroring, as phrases in the accompaniment are immediately followed by their inversions. This particular piece was dedicated to the memory of Claude Debussy, whose music had a powerful effect on the younger Bartók early in the century. It was published in a collection of pieces assembled in honor of the late Debussy. It is curious to note that, despite its dedicatee, there are virtually no stylistic elements of Debussy's music found in Bartók's piece. The eighth and final Improvisation is in variation form, and echoes the structure of the first Improvisation with its three repetitions of the melody followed by a coda. As in the first piece, the last Improvisation offers a varied harmonic setting for each repetition. The first variation is a simple setting of the melody with triplets, the second a canon, the third a dense, chordal setting of the tune.
After the Improvisations, Bartók wrote almost no piano music between 1920 and 1926. In 1926, the so-called "piano year," Bartók began writing for the instrument again, in part to fulfill his own repertoire needs as a touring concert pianist.