Polytonality

thumb|upright=1.5|Example of C and F major chords together in Igor Stravinsky|Stravinsky's Petrushka (see: [[Petrushka chord)File:Stravinsky-petrushka-fanfare.mid]]Polytonality (also polyharmony) is the musical use of more than one key simultaneously. Bitonality is the use of only two different keys at the same time. Polyvalence or polyvalency is the use of more than one harmonic function, from the same key, at the same time.