1) Music 2) Polytonalism 1) Polytonalism 
Polytonality (also polyharmony (Cole & Schwartz)) is the musical use of more than one key simultaneously. Bitonality is the use of only two different keys at the same time. Polyvalence is the use of more than one harmonic function, from the same key, at the same time (Leeuw 2006, 87). Some examples of bitonality superimpose fully harmonized sectio...
in music, the simultaneous occurrence of two or more different tonalities or keys (the interrelated sets of notes and chords used in a composition). ... [4 related articles]
[n] - music that uses two or more different keys at the same time
The use of two different keys simultaneously. Despite much loose talk, true polytonality is rare. Upper structures (q.v.) and outside playing do not usually qualify because there is always a strong single underlying tonality.
polytonalism noun music that uses two or more different keys at the same time
Combination of two or more keys being played at the same time.