Tetrachords, Scales, and Modes: Answer to a Student Question

Hey there folks, I got some more theory for you today.  Yipee!

The following is a question and answer thread from my YouTube channel, regarding my video about how to quickly visualize any major scale on your keyboard, by using something called the major tetrachord.  First, the original video, and then the Q&A.

Student: Is there something that is just as easier to use to identify minor scales?
Me: Thanks for your question! I will answer in terms of the “natural minor,” although this answer applies to the harmonic and melodic minor scales as well. First of all, the standard minor scales, as well as each of the “modes” of the major scale (dorian, mixolydian, etc), can all be broken up into tetrachords. The bad news is, the lower tetrachord of a minor scale has a different whole-step/half-step pattern than the upper tetrachord. (The cool thing about the major scale, on the other hand, as I describe in this video, is that the lower and upper tetrachords have the same pattern.) You may still find it helpful to break any scale type into two tetrachords. I hope this helps!
Student: Thank you for your reply. Do you have any videos going through each modes (Lydian, Mixolydian etc) and the easiest way to identify them using the tetrachords? Different modes have different patterns.
Me: I don’t have any videos on that yet. When I get a chance I will make a blog post (soon) on pianowithkent.com, which will give a description of my own approach to memorizing the modes. Meantime, try using C-major as your master reference. Starting there, realize that the modes of C Major all share the same pitches as C-major (the white keys of the piano). That is, Dorian mode of C Major starts on D. Phrygian starts on E. Lydian, on F. Mixolydian, on G. Aolian (aka the natural minor scale) starts on A. And finally, Locrian, which starts on B. Since these are all the modes of C major, they all use just the white keys of the piano. Use these modes as your master reference to building any given mode starting on any note. It helps to attack the problem from several angles. One angle is to break up each mode’s unique pattern into two successive tetrachords. Another is to be able to find the major scale (the parent scale) associated with the mode you want. For example, E-flat Dorian is the “Dorian mode of D-flat Major.” (By definition, they share the same pitches). Yet another angle is to become a master of every major scale and every natural minor. Then learn the modes as distinct variations of either the major or the minor. For example, Mixolydian is simply a major scale with a flatted seventh. This last approach is the one that I find easiest But in different contexts I use all these approaches. As far as the modes go, focus on Dorian, Mixolydian and Lydian. These are by far the most commonly used modes.