Post by Andy Evans
Tonal music revolves around a single tonal centre - most "classical" music. Bitonal superimposes one key on another and has become increasingly widely used in post-bop jazz improvisation. Polytonal just extends this to more than 2 tonal centres.
I started asking myself why Keith Jarrett is a more interesting improvisor than Bill Evans, whose improvisations can be more bland as a whole. Both exquisite craftsmen but polytonal has more spice to the dish. As a fan of Stravinsky I really enjoyed this YT analysis of how he constructed his harmonies by superimposing one key on another. Once you tune into this it kind of hooks you.
This reminds me of my music graduate studies when questions of
polytonality were explained as expressions of octatonic pitch
collections, although the interplay with other scales was also considered.
I see this view is now being reconsidered:
Dmitri Tymoczko; Stravinsky and the Octatonic: A Reconsideration
The importance of the octatonic scale in Stravinsky's music has
consistently been overstated. While octatonicism is an aspect of
Stravinsky's technique, it is just one of a number of different
components that jointly produce the "Stravinsky sound." The article
focuses on two techniques that have often been mistaken for
octatonicism: modal uses of the non-diatonic minor scales; and the
superimposition of elements that belong to different scalar collections.