Title:           Music Theory Lecture Three, part 1: Modes
Author:          Anonymous
Pastebin link:   http://pastebin.com/ck0THV4B
First Edit:      Friday 10th of May 2013 05:22:52 PM CDT
Last Edit:       Friday 10th of May 2013 05:22:52 PM CDT

Now that we have the diatonic scale. We're going to be looking at the modes of the scales, and how the modes are constructed.
 
        There are seven modes in total: ionian, dorian, phrygian, lydian, mixolydian, aeolian, and locrian. The ionian is just another name for the major scale, and aeolian is just the natural minor scale. Each mode is composed of two tetrachords combined by either a halfstep, or wholestep. We're going to look at the modes in two different ways. In one, we'll use C as the starting pitch for each mode, so you can see each mode differs, and in the other, use the key of C major (no sharps or flats) to show how the modes relate to each other. We'll start off with key of C major.
 
        C D E F G A B C
 
        The first tetrachord is going to be C D E F, and the second will be G A B C. The intervals of the first tetrachord are WWH. A wholestep between C and D (W), a wholestep between D and E, and a halfstep between E and F (H). So, it's two wholesteps, and a halfstep, WWH. This is a major tetrachord (M). Now, let's look at the next tetrachord, G A B C. It's the same thing. A wholestep between G and A, a wholestep between A and B, and a halfstep between B and C, WWH. So, now we have two tetrachords WWH and WWH, but there's an interval missing: the F to G. There's a wholestep between the two that connects the two tetrachords. When we put those together, we have WWH-W-WWH. The ionian mode is made of two major tetrachords with a wholestep in between them.
 
        The next mode, dorian, is two minor tetrachords (m) with a wholestep in between. Dorian used to be the typical minor key, but eventually aeolian became the minro. A minor tetrachord is WHW, instead of WWH. A dorian mode would look like this: WHW-W-WHW. If we want to stay in the key of no sharps or flats, we'll need to start the mode on D (D E F G A B C D). D up a wholestep is E. E up a halfstep is F, and F up a wholestep is G (WHW). The next tetrachord is A B C D. A to B is another wholestep. B to C is a halfstep, and C to D is a wholestep (WHW). The connecting interval is from G to A, which is a wholestep.
 
        The next mode starts on E, and is the phrygian mode. The phrygian is made of two phrygian tetrachords (ph) and a wholestep connecting the two. A phrygian tetrachord is HWW, so the mode would look like this HWW-W-HWW. E to F is a halfstep, F to G is a wholestep, G and G to A is a wholetep (HWW). B to C is a halfstep, C to D is a wholestep, and D to E is a wholestep, with the connecting interval from A to B being a wholestep.
 
So far, we have three different modes, and three different kinds of tetrachords:
 
M+M=ionian
 
m+m=dorian
 
ph+ph=phrygian
 
        Moving onto lydian. Lydian is made of a wholetone tetrachord (Wt), and major tetrachord with a halfstep connecting the two instead of a wholestep like the previous modes. A wholetone tetrachord is made of three wholesteps (WWW). Lydian is going to start on F. F to G is a wholestep, G to A is a wholestep, and A to B is a wholestep. The next tetrachord is major, and starts on C. C to D is a wholestep, D to E is A wholestep, and E to F is a halfstep. The connecting interval between B and C is a halfstep, so the mode would look like this, WWW-H-WWH.
 
        Mixolydian is the next mode, and it's made of a major, and a minor tetrachord, with a wholestep connecting the two (WWH-W-WHW). This mode will start on G. G to A is a wholestep, A to B is a wholestep, and B to C is a halfstep. The connecting interval being C to D is a wholestep, leads us to the next tetrachord. D up a wholestep is E, which up a halfstep is F, and up a wholestep is back to G.
 
        The last mode we'll learn about is the aeolian, which is commonly known as the natural minor scale. The aeolian mode is made of a minor tetrachord and a phrygian tetrachord, with a wholestep connecting the two (WHW-W-HWW). This one will start on A. A to B is a wholestep, B to C is a halfstep, and C to D is a wholestep. E to F is a halfstep, F to G is a wholestep, and G to A is a wholestep, with the wholestep from D to E being the connecting interval.
 
So, to review the modes and tetrachords:
WWH=Major
WHW=minor
HWW=phrygian
WWW=Wholetone
 
M+M=ionian
m+m=dorian
ph+ph=phrygian
Wt+M=lydian
M+m=mixolydian
m+ph=aeolian.
 
We aren't going to do locrian, because it's never used, but if you want to figure it out yourself, go for it.