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I've been learning about music theory for quite some time now, and I've been wondering. How does one determine the modes of the sharps and flats?

For instance, what is the mode for C#, D#, F#, G#, and A#.

I know that C is Ionian, D is Dorian, E is Phrygian, F is Lydian, G is Mixolydian, A is Aeolian and B is Locrian.

But what about the sharps? Is there a specific mode for each of the sharps, and do they exist for their enharmonic equivalents?

Please let me know...

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  • You only have 5 tones, but Church modes have 7. What are the other two tones, the E and B? Jul 18, 2022 at 13:18
  • You've listed the "white key" modes. The modes based on the key of C major. They are not THE modes but are commonly used as a teaching device without elaboration, which may explain the confusion here.
    – Awalrod
    Jul 18, 2022 at 13:32

6 Answers 6

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A mode is a specific arrangement or set of intervals around a root pitch. For example a Dorian mode is one where, relative to a root pitch, there are the intervals:

  • 1st degree (root) : +0 semitones
  • 2nd degree : +2 semitones
  • 3rd degree : +3 semitones (minor third)
  • 4th degree : +5 semitones
  • 5th degree : +7 semitones
  • 6th degree : +9 semitones (major sixth)
  • 7th degree : +10 semitones (minor seventh)

Because Ionian, Dorian, Phrygian, Lydian etc. can be obtained as rotations of the diatonic major scale, they are said to be modes of the major scale. There are modes of non-diatonic scales such as the melodic minor scale as well.

C is not Ionian, but the mode of C major starting from C as the root is C Ionian. Here are the rest of the diatonic modes with C as the root:

C modes

In the picture above, what is the difference between C Ionian and C Lydian? Then look at F Ionian and F Lydian:

F modes

Same difference! In Lydian, the fourth scale degree is sharpened compared to the Ionian mode.

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All of the modes — Major, Dorian, Phrygian, etc. — can start on any key. Using major as the starting point, then the "first" mode is major, the "second" mode is Dorian, the "third" mode is Phrygian, etc. Modes use a common key signature but differing tonic pitches.

For example, if I begin with C# major, then I will have, corresponding to that key signature, D# dorian, E# phrygian, and so forth. From D major, I have E dorian, F# phrygian, ....

The sharps and flats are no exception. Any scale can start on a black key or a white key.

If one plays only the black keys, as expressed in the question (C# D# F# G# A#), the result is known as a pentatonic scale: specifically, the third mode of the F# major pentatonic scale. Pentatonic scales, as any other scale, may start on any key, black or white. A C major pentatonic would be C D E G A, C# major pentatonic would be C# D# E# G# A#, D major pentatonic is D E F# A B.

Search this site for "pentatonic" for many posts on that topic.

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  • Hey that was really helpful and it makes sense. I had no idea that's how it worked. But then what about modes like Phrygian Dominant? Is that still the Phrygian scale with some sort of change to the dominant scale degree? Jul 18, 2022 at 5:05
  • The "diatonic modes" are the ones I described above. For a given key signature, each mode contains the same pitches, just with a different tonic pitch. "Phrygian dominant", so named because it contains a b2 and b7, is an unrelated scale that, while it is a mode of the ascending melodic minor scale, finds its true origins in Middle Eastern music.
    – Aaron
    Jul 18, 2022 at 5:17
  • @Aaron - My understanding is that the Phrygian dominant scale is a mode of the harmonic minor scale, not a melodic minor scale, thanks to its use of both b2 and plain old non-flattened 3.
    – Dekkadeci
    Jul 18, 2022 at 17:56
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Your third paragraph is true, but only holds for key C.

Instead of using C = Ionian, D = Dorian, etc., you need to think Ionian =^1, Dorian =^2, Phrygian =^3 (^ means note, becoming root of the mode) and so on. So for key C♯, for example, C♯ is root of C♯ Ionian, D♯ is root of D♯ Dorian, and so on.

When you get to the flats (you will eventually!), the same applies. In key A♭, for example (4♭) A♭ is the root (tonic) of A♭ Ionian, B♭ Is the root of B♭ Dorian, etc.

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In addition to the other answers here, it can help to think of modes in terms of "brightness":

-Brightest-

Lydian

Ionian

Mixolydian

Dorian

Aeolian

Phrygian

Locrian

-Darkest-

Each mode in this ordering has one more flat or one fewer sharp (as applicable) than the mode above it.

Note that every mode except locrian is adjacent to either ionian or aeolian, and can be defined in relation to one of them by one raised or lowered tone.

How do you know which tone changes? It's the same order of sharps/flats as key signatures! For example, let's say we're in the key of D, where dorian is the one with no sharps or flats. Then we add sharps as we traverse the list upwards:

D mixolydian has F#;

D ionian has F# and C#;

D lydian has F#, C#, and G#.

We can't keep going because the next sharp is D, which is our root.

Your question about translating sharps to modes can't directly be answered because every key has multiple enharmonic equivalents. But if you know the number of sharps and the mode, you can start at that mode on the list and count down until you get to 0 sharps. 5 sharps and lydian mode? 5 places down from lydian is phrygian, and the root of the natural phrygian scale is E, so you know you're in E lydian.

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Check out my javascript modes app.

No download - just visit this address: https://b-p-thomas.github.io/ and the app runs in the web page.

Use it to read off the notes you have in a particular mode.

enter image description here

In the snap above, the solid blob is next to Bb and you can read off the notes in Bb mixolydian by going clockwise round the dial reading the letter name next to each blob.

The light gray blob shows you the major scale containing the notes of the mode. In the snap, Bb mixolydian contains the same notes as Eb major.

The important thing is that all major modes have the same pattern of intervals - I've shaded the semitone intervals to make them more obvious.

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  • Don't all modes, minor inc., have the same pattern as each other? TTSTTTS, just starting somewhere else in that sequence?
    – Tim
    Jul 18, 2022 at 15:37
  • @Tim - I was very careful to say major modes. One counter-example to your question - a harmonic minor scale doesn't have that TTSTTTS pattern, so any mode constructed from it won't either. Jul 18, 2022 at 16:19
  • Ah, I see now. It was just that the question, the OP, and all the answers only referred to major keys and their modes (which of course inc. natural minor). Didn't want OP to get too befuddled..!
    – Tim
    Jul 18, 2022 at 16:24
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For instance, what is the mode for C#, D#, F#, G#, and A#.

I know that C is Ionian, D is Dorian, E is Phrygian, F is Lydian, G is Mixolydian, A is Aeolian and B is Locrian.

The modes are associated with the given pitches through this algorithm:

To play a given mode, find the associated key on the keyboard, then find the one an octave higher or lower, and then play all the white keys between them, inclusively.

It is impossible to do this with any black key.

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