The concept of a pitch axis is that rather than having chords I through vii, every chord centres around a single pitch or note. While most music in the diatonic system has a root that is often visited, with a pitch axis the root is very strongly emphasised. Similar to how jazz musicians can consider scales on a chord by chord basis the scale that is used over each bar of the pitch axis is often based on the chords played with the pitch axis root in every chord.
A simple example is shown here
Like the Video, Try playing a note( low E on guitar is good or middle c for pianists) then play a mode based on that note, like E minor followed by E major, then e phrygian,superlocrian,neopolitan,Hindustan,enigmatic etc
Like the video this often works better if the pitch axis is played as a drone/long note
Vai satriani’s and petrucci all use this as it adds a lot of harmonic interest and can be done on many levels of complexity. Changing from minor aolean to Dorian to melodic minor to major only changes one note in each scale per switch, but the mood and flavour of the sound changes noticeably.
I’ve noticed that a great place to do such a change, that’s not specifically a pitch axis, is during a key change. The music has transitioned so much anyway that the new mode is a little bit extra that emphasises this change and allows you to add more texture to the song.
Switching modes in this way is undeniably tricky and involves knowledge of every mode, for piano this may be easier but I suggest playing around with it. If you want to use chords your ears are your friends in finding a set of modal chords that sound appropriate to what you’re playing be it consonant or dissonant.
So in summary
Level 1 is modes over a drone
Level 2 is modes over chords
Level 3 is in isolation in a section of music
Level 4 is using them to emphasise changes and transitions in the music
Why this concept is so powerful is that you can decide how little or much to use it, which will dictate how subtle the mood change is. Check out Bjork for an example of how showy this Can be: Aeroplane
It takes your ears to get something that’s got a good balance, but here’s a (VERY) rough piece I threw together based off of G Phrygian,Ionian,lydian and dorian.
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