The psychological effect that polytonality can have on the listener is often governed by the relationship between the keys that are presented. Vincent Persichetti elaborates:
“The fundamental quality of polytonal texture is determined by the key relationship set up by the tonics. In major-key combinations, a polytonal order of tension from consonant to dissonant is secured by combining two keys that lie a perfect fifth, major ninth, major sixth, major third, major seventh apart – and so on up the cycle of fifths . . . Those keys that are not closely related according to the circle of fifths will more easily set apart the tonal key spheres.” 1
The following is an elaboration of Persichetti’s visual representation of his theory with regard to the consonance or dissonance of key combinations:
Although the case can be made that this is a subjective classification system, and although Persichetti does not provide a definition of or reasoning with regard to how he defines resonance within the confines of polytonality, the examples provided in the chapter of his book display a thorough understanding of his experience with polytonality. If I can offer a criticism, it is that I feel as if Persichetti could have provided a much more in depth analysis of why certain key relationships are more consonant, dissonant, or resonant than others, rather than mere stating that this is so.
1 Persichetti, Vincent, “Polytonality.” Twentieth-Century Harmony: Creative Aspects and Practice. New York: Norton, 1961, p. 255-261.