Using Modal Harmony

Hi everyone, I was wondering if anyone had some views on the use of modal harmony in orchestral music. I'm trying to figure out how composers like Vaughan Williams use modal harmony on his works, partically in The London Symphony. I know he bases his ideas a lot on traditional old folk roots (lots of parallels) and also the use of orchestration helps to bring his ideas even more intrincating. So my questions are: Does anyone have any suggestion on how to modulate in the modal language that he uses? Any way to plan modulations and chord substitution between modes without sounding "jazzy"? What's your opinion on this approach to harmony? Also use a lot by film composers like Harry Gregson Williams, John Williams (I should change my surname to Williams too see if it helps!) and Joseph Loduca. I just would love to see what people have to say about it. Thanks.

In some modes, particularly lydian and dorian, it's very easy to borrow chords from the equivalent major/minor scale of the same tonic because the modes are so similar to the scale itself. Since our ear is so familiar with both modulating is a very simple task that can be approached pretty much in the same way as if there were no mode. The interesting thing about dorian is that we have a stronger route to the subtonic via the major IV chord.

Slipping into modes isn't a particularly jazzy process and usually doesn't sound like one unless there's a lot of emphasis on jazzy articulation in the melody, or jazzy additions to the harmony, or very jazzy rhythms, or any combination.

Modal harmony is fun, but you have to take a moment always to consider the scale and the triads at your disposal and how they're different versus just a normal major or minor scale. If the tonic is clear then often substitutions can be easy, like substituting in a minor iv or major VI chord in dorian. Sometimes the tonic might even sound a bit uncertain, like in phrygian, which would also add a very Spanish tone to a piece (Iberia by Albeniz is a classic example).