Confused on Modes and Key Signatures, bleh


So from what I understand, there are major and minor key signatures. A piece of music in C major, for instance, would have the same set of notes as its relative minor, the A minor. When seen on a music sheet, the key signature should be the same (with no sharps or flats), but depending on where the “tonal center” is, the music could either be in the key of C major or A minor.

What if the musical piece’s tonal center is in E, as in E Phrygian? There would be lots of E minor triads and the music would continually resolve to the E note. The key signature would still be the same as C Major or A minor (no flats or sharps), but what key would you now say the music is now in? From what I understand, E Phrygian is just a mode, so one would not say the music is in the key of E Phrygian.

Please help clarify this confusion.



It’s definitely not in the key of E Phrygian. (As you indicate, there are only two modes that have been promoted to “key” status: Ionian and Aeolian.)

So there are two options: you think of it as being in C Major or A Minor; or you think of it as being in the corresponding major or minor key with the same root (in this case, E Minor) and then use accidentals throughout to get the right notes.

I know that notation wise, I have seen it written out both ways. Say you have a Mixolydian fiddle tune, like Red Haired Boy, and it’s in G Mixolydian. You could write it out in G Major and in every measure you put a natural on the F# to bring it down to F. Or you could write it out in C Major/A Minor. I’ve seen tunes like this written out either way. I don’t know which way is Officially Right when talking about a piece at a theory level, but you definitely see it written out both ways in notation.


The key signature on the sheet music would be C major/A minor but it wouldn’t have a “key”, it would be referred as a modal piece in E phrygian.

I had a sort of similar issue with this last week. I was analyzing the verse of a song (Am - D - G - C - F#ø - B7 - Em - E7) and wasn’t sure if it was A dorian or E minor. I was leaning towards dorian because the tonal center seemed to be A and it started with Am. Was the B7 tonicizing the Em or E7 tonicizing Am? Ended up it was in E minor because the only non-diatonic melody note was F (dorian mode would be F#) and it was played over the Am chord, so it definitely wasn’t dorian.

Second verse was cool because it used the Neapolitan chord and modulated to phrygian for a couple of bars before the chorus.


Excellent explanation. Thanks for clarifying!!


Thanks for this, Ian!


It is interesting that that two modes that enjoy the status of “key” are probably the crappiest sounding ones (Ionian in particular is unbearable to my ears in most cases).


Great question! I’ve done it both ways in our tablature. Honestly, I think best answer is the practical one. If you’re writing notation, do whatever results in the fewest accidentals in the measures themselves. If you write something in E major and then add accidentals to get E Phrygian dominant, it looks crazy and gets hard to read. Instead, A minor / C major would much simpler - you only need G#.

If you really think about it, nobody can tell from looking at a key signature what the actual “key” of a piece is anyway, because as you point out, it could be major or minor. So there really is no point to doing it any other way.

For the reasons above, a mode is as good as a “key” to me in actual practice, because the key signature of D aeolian is the exact same as F major and so on.


if you find yourself on certain forums you can get shouted down for assuming that Major = Ionian lol. of course, I try to avoid those forums but some bad memories remain hehe


Thanks Troy for your inputs!


I think there’s a reason for that and you probably won’t learn about it from theory books. My response will be based completely on my own experience in hearing, playing and analysing various kinds of music, so many people may disagree.
If you look at the scales we use to create chords, they’re usually…
-ionian or its modes
-melodic minor or its modes
-harmonic minor or its modes
-harmonic major or its modes
-halfstep - wholestep or wholestep - halfstep scale
-whole tone scale
-minor 3rd-halfstep or halfstep-minor 3rd scale
These scales have something very important in common. There are never two halfsteps in a row in them. For some reason our ears make us gravitate towards that kind of harmonical tools. Somebody may say there is stuff like bebop scale or double harmonic major. Yes, but they’re used to create melodies, not chords. How often do you hear a Cmaj7(b9) chord? Probably not so often, because maj7-root-b9 create a cluster.
The problem I see with those chords is, any cluster destroys delivered harmonical information. Notes start to sound unimportant to me, chord tones doesn’t sound strong anymore, etc. Jazz players can outline chords playing single note lines, if you try to outline Cmaj7b9 playing b9 on strong parts of the beat or something, probably nobody will actually hear it as Cmaj7b9.
Now back to why certain stuff sounds “tonical”. We don’t hear chords as single entities, they’re all connected to each other, it’s like our brain records harmony and then compares it to what comes next. Basic I, IV, V chords built on C ionian contact half step away in important places, even when certain notes aren’t played together in the same place of the bar.
I - C E G - E note, 3rd is “destroyed” by F note - root of IV chord - that’s why I and IV serve as different functions (tonic vs subdominant)
V - G B D - B note, 3rd is “destroyed” by C note - root of I chord that’s why I and V serve as different functions (tonic vs dominant)
If I play C major and then any chord from C ionian that includes F, I feel like there’s something happening and there’s a function change. What I’m saying may be not so convincing for now, but let’s investigate further.
Ionian, melodic minor, harmonic minor, harmonic major have something else in common. They have perfect 4th and perfect 5th inside. That probably is why we say lydian is a mode of ionian, not the other way around. What happens if we try to build a I, IV, V in lydian?
I - tonic
#IV - tonic again, half diminished chord is like a tritone substitution for maj7#11 chords, most jazz guys redistribute their lydian licks over half diminished chords tritone away.
It’s impossible to build T, S, D in scales with #4 instead of natural 4.
If that’s not convincing enough, altered scale should do. Let’s say we use g altered as base.
I - tonic, G7alt
#IV - tonic again - lydian augmented, Db7#11, tritone sub, I and #IV serve the same function
That’s basically how I hear harmony. Chords are as much defined by what notes they have as what notes they don’t. Still, I’m trying a lot of weird stuff that doesn’t fit into this system, like altering roots of scales to stick b9 into chords with maj7 or to stick maj7 into chords that have min7. G altered scale b1 is Gb ionian and C ionian #1 scale is C# altered in case you’d like to try expermienting with that. I don’t really like ionian too, that’s why I’m looking for secret spices like that. Also, check out my G7#5b15 dominant
I wonder if anyone will survive the whole post.


That’s a good detailed post, but I think if you start getting into passing diminished chords between inversions of your regular minor/major 7ths you end up with something that looks like chords built off a scale with consecutive half steps (in my rudimentary understanding the Barry Harris 6th diminished scale thing is an example of this but I’m unable to give that the explanation it deserves).


Passing diminished chords really are rootless b9 secondary dominants. I’m not saying that you can’t build a song with chords whose roots move chromatically for example. It’s a common practice to do stuff like C-7 Bmaj7#11 Bb-7 Amaj7#11 Ab-7 etc etc. But if you look at each individual chord and squeeze its notes into one octave, there will be no 2 halfsteps in a row. The diminished chords are an example of this too, they’re built of minor 3rds after all.
What Bbmaj7 Bdim C-7 C#dim D-7 stems from is really Bbmaj7 G7(b9) C-7 A7(b9) D-7. 3, 5, 7, b9 of a dominant chord form a diminished7 chord. If you encounter a dominant chord and know where your 3, 5, 7, b9 are, you can start your good old yngwie diminished licks from there and it will work. Gypsy guys do it all the time.


Now I get you, sorry for muddying the waters with my other post.


No problem, I’m always curious about what other people think about my way of organizing harmony.


Diminished chords can also have a subdominant function as well. Not all of them act as 7b9 chords. Examples are I-bIII°-ii or any other #iv° Suspension that will resolve to a I Chord (usually in 2nd Inversion).
I°/biii°/#iv°/vi° are all the same chord and will resolve to the I Chord in different Inversions.

Note that for these diminished chords you would still use Harmonic Minor from the 3rd of the key.
So if you had C M7/Eb°7/Dm7 You would need the C Major Scale to play over the C M7 and the Dm7 and then E harmonic Minor to play over Eb°7.

For a dominant diminished chord that acts as a 7(b9) you just follow the same rule for secondary Dominants that lead to a minor chord: play the harmonic Minor of the chord you’re going to. So C M7/C#°7(or A7(b9b13)/Dm7 you would use D Harmonic Minor over that secondary dominant.


And that stems from II7(b9) resolving to I with V in bass instead of V. I wouldn’t be so hasty to name these chords subdominants.

If you use e harmonic minor(b phrygian dominant) it instantly defines it as B7(b9). You can use wholestep-halfstep scale, especially in an example such as Cmaj7 Eb°7 Dm7, because Em7 wasn’t played, so we aren’t sure what Eb°7 actually is. And using wholestep-halfstep keeps it that way, because it’s symmetrical and you still can’t really determine where the true root is. A pure dim7 chord can be defined only after it resolves or after you deliver enough harmonical information through melody, because it can be 4 different dominants at once.


I name them subdominant because they are neither dominant (in this function at least) nor tonic: by process of elimination it must be the only other function of chord there is: subdominant. If you also want to consider the scale degrees of the chord (#iv°) it has the scale tones #4 6 1 b3. This is very close to other subdominant chords (the ii or IV) in that it has the 4 6 and 1 (only IV has 3 in it), and because of these 2 reasons I label this chord subdominant.

Edit: Other chords that I would label subdominant would be any ivm chord as well. In C this would be Fm6/Dm7b5, Ab Maj7, Bb7(#11) to name just a few. All of these chords resolve back to C even though they aren’t V-I Cadences. (They all also take F melodic minor scale).

Yes you could also use the Diminished scale but 1. That’s atonal and is more of a special effect than anything and 2. Adds yet another scale to learn on the instrument when you really only need the Major Scale, Harmonic Minor, and Melodic Minor Scale to play over any type of changes. Also often times these #iv° chords are reharmonized as a minor ii-V in Standards. An example progression being F Maj7 - Bø E7(b9) - F Maj7 instead of F Maj7 - F°7 (or B°7. however you want to think of it) - F Maj7.

You can arrive at the conclusion of using Harmonic Minor by adjusting the Major Scale. Example still in F: F G A Bb C D E.
B°7= B D F Ab. So we need an Ab and a B.
To get this lets raise the G to G# (Ab) and Bb to B. This gives us the scale F G# A B C D E which is A Harmonic Minor.
Another option would be to instead flatten the A giving us F G Ab B C D E. This is C Harmonic Major which can also be used. Not many people know of the Harmonic Major scale or use it (and it certainly isn’t necessary to use when you can use other scales instead) but it is a good option for °7.


And that’s not a good idea imo. Just because something is not tonic and not dominant doesn’t mean it’s subdominant. That’s the problem with functional naming of things, if we were to really name all the functions we would have to connect every possible type of chord starting on every note with each other. It would be useless, because such system would take a lifetime to learn. Music is just full of unnamed functions and it will be forever, because it’s humanly impossible and redundant to name them all. It doesn’t mean everything that is not tonic and not dominant is subdominant.

That scale is far from atonal and far from special effects. It’s actually a very good choice if you have no idea what your dim7 chord is supposed to sound like, if you’re reading through a chord chard of some tune for the first time for example. Moreover, there are dominant13b9 chords. What are you going to play, mixolydian b9? Halfstep - wholestep is a way more colorful harmonical choice. You can play major triads moving up a minor 3rd, such structure can be found in this scale. You just need to learn to hear those alterations, natural13b9 and natural5#9 being the most common choice.
Also, what would you play if there was a Bdim7 chord resolving to Cmaj7, C harmonic minor?


That would be C Harmonic Major as the most obvious scale choice or A harmonic Minor.