Musical Composition, Theory and Songwriting/Modulation to unusual scales
I would like to know how one can approach the task of modulating the key of a song from a normal key/scale such as a major or minor, or perhaps a mode of the standard diatonic scale (phrygian , dorian etc), to another non-diatonic scale, for example the hirojoshi or balinese scales which have only 5 scale degrees, and is non-diatonic.
As you know, in common practice classical harmony there are rules, or at least techniques which are considered good practice, regarding modulating keys. For example it is common to modulate to distant keys using chain modulation via the circle of fifths for example.
What 'rules' or approaches are there (if any) for modulating to unusual keys where the scales are non-diatonic, or have less than 7 scale degree, such as in my examples? Thanks for your help with this unusual question :)
Hello Dale, and thank you for being patient.
There aren't any rules, for the simple reason that you've broken them by definition.
In the West from the 12th century onwards, polyphony, or combining a number of melodic strands, began to supplant monophony to a degree unmatched by any other world music. All Western music regardless of genre uses a key system that originated in the latter half of the 16th century, had completely superseded the modal system by the late 17th century, and established its rules during the 18th century. There was a certain amount of experimentation within the rules, but it wasn't until the 19th century that they were first bent, then progressively broken, until by the beginning of the 20th century they could no longer be said to apply and classical composers either made a conscious decision to return to them or attempted to formulate new systems of their own. (Popular genres - pop, heavy metal, C&W etc - never developed that far; their musical vocabulary is still pretty much in the 18th century. Jazz is more complicated in that its harmonic vocabulary is still 18th century but the individual chords have 20th century add-ons.)
The basis of the Western key system is that: the octave is divided into 12 equal semitones; the two diatonic scales, major and minor, are constructed in exactly the same way in all 12 keys; the various degrees of the scale and the triads built upon them are of greater or lesser importance in relation to the keynote; and we have the concept of "related" keys, which makes it easy to move from one key to another, either directly or via other, more closely related, keys. This is modulation, and it is the ability to modulate that makes Western music unique. So once you have firmly established your home key, you have a network of interconnections and interrelations that underpins every note you write, and it‘s the relationship between chords rather than the chords themselves that is all-important.
You're proposing to introduce non-Western elements into your composition. I know nothing about any non-Western musics but have found a useful introductory article on Balinese music: http://www.murnis.com/culture/articlebalinesemusic.htm
which makes it clear that there's a common tonal system but many distinct traditions within it, all of which have their own rules (see also http://en.wikipedia.org/wiki/Music_of_Bali
The only "rule" in Western music about incorporating a Balinese scale into your music is that you don't do it. As soon as you break the rule, you're on your own. That makes you a pioneer.
Be guided by your ears, as always in music, and if necessary formulate your own rules.
Hope this helps.