It is the use of two or more distinguishable key centers, simultaneously. However, the term bitonal can be used instead of polytonality, referring to the use of two key centers in the musical composition.
One of the most important aspects to consider, when composing in a polytonal context, is the choice of key relationships and how dissonant or consonant they will sound when juxtaposed. A consonant relationship is considered when there are at least five common pitches – i.e. C major and F major or C major and D major:
A two-voice counterpoint example using C major and D major
Accordingly, a dissonant key relationship occurs when less than five pitches are shared – i.e. C major and Ab major:
A similar two-voice counterpoint example using C major and Ab major
It is worth saying that, in consonant key relationships, if the note differences are not emphasized, like avoiding the Bb or a B natural in a F major and C major relationship, then we are no longer in a polytonal context. And, when working in dissonant key relationships, it is important to establish the respective tonal centers so that the premise of a polytonal context is fulfilled, that is, to simultaneously have two or more distinguishable key centers.
There are some considerations to keep in mind when composing with polytonal materials:
- Separation of keys by register, allowing for each key to be heard distinctly:
- Strong chord progressions that highlight the respective tonal center from each key and emphasize the different notes from each key:
- Avoiding many modulations that can confuse and weaken the initial key relationships
- When modulations occur in one of the key centers, it is customary to maintain the same pitch center – i.e. from C major to C minor:
- Avoiding the use of chromatically altered chords since these chords make sense when working in a single tonality and thus, it is not necessary to introduce more chromaticism than the one existing in the polytonal context.
- Working with three or more key centers makes the separation of each tonality harder to achieve. In this case, it is suggested that the clear separation of at least one key center is achieved
- Using counterpoint can be an effective way of working with two and more key centers since each melodic voice separates the respective tonal material:
Example with four voice polytonal counterpoint – from the top down, voice one in C major is doubled by the second voice in D major. Voice three is in F# major and voice four in E major
Polytonality presents itself as another way of extending and exploring tonality in more varied ways, like composing chromatic passages without resorting to functional chromaticism.
However, as suggested before, you should be the one to evaluate the purposes of this composition technique for your work in the sense that it is not mandatory to follow the presented suggestions if the aim is to create a chromatic chaos effect, for example.
It is the simultaneous use of two or more distinguishable modal centers from the same or different key centers. The modal centers may have the same root, like a C Dorian with C lydian; or with different roots, like C dorian and G lydian:
Example with C Dorian and C Lydian
Similar example with C Dorian and G Lydian
The same consonant and dissonant guidelines for choosing the key center relationships and the suggested ways of working with the different key centers when working with polytonality still apply to polymodal work. However, keep in mind that modal harmony tends to be more static and does not work in the same way that functional harmony does.
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