In the piece there are three “pitch worlds” requiring different precision of intonation: sounds of natural row (most exact in intonation), fine tempered sounds and “affects” (most free in pitch).
The choice and the comparing of different pitch phenomena defines the change of the expression and the timbre. Natural intervals are very clear; they have no beats. So an interpreter, hearing and playing in natural scale strives to intonate tones more “carefully”, thin, clear and without vibrato.
In the equal tempered scale all major intervals are expanded, all minor are constricted, and all leading tones are approached to their resolutions. String players often yet more accentuate this trend when they play sharp notes higher than enharmonically equal flat notes. This way performers intensify an expression of the pitch system. So equal tempered scale is very expressive: especially the resolutions of the leading tones. At the same time all consonants are not so clear. Consequently more important elements become an expressive melody with semitones, chromatisms, verticality built not on consonants but on resolutions.
These differences in pitch hearing engender different harmony and texture style, different performance manner, and the properties of instruments' structure.
Thus, the problem of different pitch system transits to aesthetical problems. This feature describes much in the evolution from musical style of XVII century to style of XIX.
This correlation of different aspects of music (pitch, expression, manner, timbre, aesthetical aspect) in many ways is an artistic problem of this piece. Not a polystylistic, but superfine playing with musical phenomena.